Expandable reamer for subterranean boreholes and methods of use

ABSTRACT

An expandable reamer apparatus and methods for reaming a borehole are disclosed, including at least one laterally movable blade carried by a tubular body selectively positioned at an inward position and an expanded position. The at least one laterally movable blade, held inwardly by at least one blade-biasing element, may be forced outwardly by drilling fluid selectively allowed to communicate therewith or by at least one intermediate piston element. For example, an actuation sleeve may allow communication of drilling fluid with the at least one laterally movable blade in response to an actuation device being deployed within the drilling fluid. Alternatively, a chamber in communication with an intermediate piston element in structural communication with the at least one laterally movable blade may be pressurized by way of a movable sleeve, a downhole turbine, or a pump.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/999,811, filed Nov. 30, 2004, now U.S. Pat. No. 7,549,485, issued Jun23, 2009, which is a continuation-in-part of U.S. patent applicationSer. No. 10/624,952, filed Jul. 22, 2003, now U.S. Pat. No. 7,036,611,issued May 2, 2006, entitled EXPANDABLE REAMER APPARATUS FOR ENLARGINGBOREHOLES WHILE DRILLING AND METHODS OF USE, which claims the benefit ofU.S. Provisional Patent Application Ser. No. 60/399,531, filed Jul. 30,2002, entitled EXPANDABLE REAMER APPARATUS FOR ENLARGING BOREHOLES WHILEDRILLING AND METHOD OF USE, the disclosure of each of which isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an expandable reamerapparatus and methods for drilling a subterranean borehole and, morespecifically, to enlarging a subterranean borehole beneath a casing orliner. The expandable reamer may comprise a tubular body configured withmovable blades that may be displaced generally laterally outwardly, themovable blades having cutting elements attached thereto.

2. State of the Art

Drill bits for drilling oil, gas, geothermal wells, and other similaruses, typically comprise a solid metal or composite matrix-type metalbody having a lower cutting face region and an upper shank region forconnection to the bottom hole assembly of a drill string formed ofconventional jointed tubular members, which are then rotated as a singleunit by a rotary table or top drive drilling rig or by a downhole motorselectively in combination with the surface equipment. Alternatively,rotary drill bits may be attached to a bottom hole assembly, including adownhole motor assembly, which is in turn connected to an essentiallycontinuous tubing, also referred to as coiled or reeled tubing, whereinthe downhole motor assembly rotates the drill bit. The bit body may haveone or more internal passages for introducing drilling fluid or mud tothe cutting face of the drill bit to cool cutters provided thereon andto facilitate formation chip and formation fines removal. The sides ofthe drill bit may typically may include a plurality of laterallyextending blades that have an outermost surface of a substantiallyconstant diameter and generally parallel to the central longitudinalaxis of the drill bit, commonly known as gage pads. The gage padsgenerally contact the wall of the borehole being drilled in order tosupport and provide guidance to the drill bit as it advances along adesired cutting path or trajectory.

As known within the art, blades provided on a rotary drill bit may beselected to be provided with replaceable cutting elements installedthereon, allowing the cutting elements to engage the formation beingdrilled and to assist in providing cutting action therealong.Replaceable cutters may also be placed adjacent to the gage area of therotary drill bit and sometimes on the gage thereof. One type of cuttingelement, referred to variously as inserts, compacts, and cutters, hasbeen known and used for providing the primary cutting action of rotarydrill bits and drilling tools. These cutting elements are typicallymanufactured by forming a superabrasive layer or table upon a sinteredtungsten carbide substrate. As an example, a tungsten carbide substratehaving a polycrystalline diamond table or cutting face is sintered ontothe substrate under high pressure and temperature, typically about 1450°C. to about 1600° C. and about 50 kilobars to about 70 kilobars pressureto form a polycrystalline diamond compact (“PDC”) cutting element or PDCcutter. During this process, a metal sintering aid or catalyst such ascobalt may be premixed with the powdered diamond or swept from thesubstrate into the diamond to form a bonding matrix at the interfacebetween the diamond and substrate.

Further, in one conventional approach to enlarge a subterraneanborehole, it is known to employ both eccentric and bicenter bits toenlarge a borehole below a tight or undersized portion thereof. Forexample, an eccentric bit includes an extended or enlarged cuttingportion that, which that, when the bit is rotated about its axis,produces an enlarged borehole. An example of an eccentric bit isdisclosed in U.S. Pat. No. 4,635,738 to Schillinger et al., assigned tothe assignee of the present invention. Similarly, a bicenter bitassembly employs two longitudinally superimposed bit sections withlaterally offset axes. An example of an exemplary bicenter bit isdisclosed in U.S. Pat. No. 5,957,223 to Doster et al., also assigned tothe assignee of the present invention. The first axis is the center ofthe pass-through diameter, that is, the diameter of the smallestborehole the bit will pass through. Accordingly, this axis may bereferred to as the pass-through axis. The second axis is the axis of thehole cut in the subterranean formation as the bit is rotated and may bereferred to as the drilling axis. There is usually a first, lower andsmaller diameter pilot section employed to commence the drilling, androtation of the bit is centered about the drilling axis as the second,upper and larger diameter main bit section engages the formation toenlarge the borehole, the rotational axis of the bit assembly rapidlytransitioning from the pass-through axis to the drilling axis when thefull diameter, enlarged borehole is drilled.

In another conventional approach to enlarge a subterranean borehole,rather than employing a one-piece drilling structure, such as aneccentric bit or a bicenter bit to enlarge a borehole below aconstricted or reduced-diameter segment, it is also known to employ anextended bottom hole assembly (extended bicenter assembly) with a pilotdrill bit at the distal end thereof and a reamer assembly some distanceabove. This arrangement permits the use of any standard rotary drill bittype, be it a rock bit or a drag bit, as the pilot bit, and the extendednature of the assembly permits greater flexibility when passing throughtight spots in the borehole, as well as the opportunity to effectivelystabilize the pilot drill bit so that the pilot hole and the followingreamer will traverse the path intended for the borehole. This aspect ofan extended bottom hole assembly is particularly significant indirectional drilling.

The assignee of the present invention has, to this end, designed asreaming structures so-called “reamer wings,” which generally comprise atubular body having a fishing neck with a threaded connection at the topthereof and a tong die surface at the bottom thereof, also with athreaded connection. U.S. Pat. Nos. 5,497,842 to Pastusek et al. and5,495,899 to Pastusek et al., both assigned to the assignee of thepresent invention, disclose reaming structures including reamer wings.The upper midportion of the reamer wing tool includes one or morelongitudinally extending blades projecting generally radially outwardlyfrom the tubular body, the outer edges of the blades carrying PDCcutting elements. The midportion of the reamer wing also may include astabilizing pad having an arcuate exterior surface having a radius thatis the same as or slightly smaller than the radius of the pilot hole onthe exterior of the tubular body and longitudinally below the blades.The stabilizer pad is characteristically placed on the opposite side ofthe body with respect to the reamer blades so that the reamer wing toolwill ride on the pad due to the resultant force vector generated by thecutting of the blade or blades as the enlarged borehole is cut. U.S.Pat. No. 5,765,653 to Doster et al., assigned to the assignee of thepresent invention, discloses the use of one or more eccentricstabilizers placed within or above the bottom hole reaming assembly topermit ready passage thereof through the pilot hole or pass-throughdiameter, while effectively radially stabilizing the assembly during thehole-opening operation thereafter.

Conventional expandable reamers may include blades pivotably or hingedlyaffixed to a tubular body and actuated by way of a piston disposedtherein as disclosed by U.S. Pat. No. 5,402,856 to Warren. In addition,U.S. Pat. No. 6,360,831 to Åkesson et al. discloses a conventionalborehole opener comprising a body equipped with at least twohole-opening arms having cutting means that may be moved from a positionof rest in the body to an active position by way of a face thereof thatis directly subjected to the pressure of the drilling fluid flowingthrough the body.

Notwithstanding the prior approaches to drill or ream a larger-diameterborehole below a smaller-diameter borehole, the need exists for improvedapparatus and methods for doing so. For instance, bicenter and reamerwing assemblies are limited in the sense that the pass-through diameteris nonadjustable and limited by the reaming diameter. Further,conventional reaming assemblies may be subject to damage when passingthrough a smaller-diameter borehole or casing section.

BRIEF SUMMARY OF THE INVENTION

The present invention generally relates to an expandable reamer havingmovable blades that may be positioned at an initial smaller diameter andexpanded to a subsequent diameter to ream or drill a larger-diameterborehole within a subterranean formation. Such an expandable reamer maybe useful for enlarging a borehole within a subterranean formation,since the expandable reamer may be disposed within a borehole of aninitial diameter and expanded, rotated, and longitudinally displaced toform an enlarged borehole therebelow or thereabove.

In one embodiment of the present invention, an expandable reamer of thepresent invention may include a tubular body having a longitudinal axisand a trailing end thereof for connecting to a drill string. Theexpandable reamer may further include a drilling fluid flow pathextending through the expandable reamer for conducting drilling fluidtherethrough and a plurality of generally radially and longitudinallyextending blades carried by the tubular body, carrying at least onecutting structure thereon, wherein at least one blade of the pluralityof blades is laterally movable. Further, the expandable reamer mayinclude at least one blade-biasing element for holding the at least onelaterally movable blade at an innermost lateral position with a force,the innermost lateral position corresponding to an initial diameter ofthe expandable reamer and a structure for limiting an outermost lateralposition of the at least one laterally movable blade, the outermostlateral position of the at least one laterally movable bladecorresponding to an expanded diameter of the expandable reamer. In oneembodiment, an expandable reamer may include an actuation sleevepositioned along an inner diameter of the tubular body and configured toselectively prevent or allow drilling fluid communication with the atleast one laterally movable blade in response to an actuation deviceengaging therewith.

For example, the expandable reamer of the present invention may includean actuation sleeve, the position of which may determine deployment ofat least one movable blade therein as described below. For instance, anactuation sleeve may be disposed within the expandable reamer and mayinclude an actuation sleeve positioned along an inner diameter of thetubular body and configured to selectively prevent or allow drillingfluid communication with the at least one laterally movable blade inresponse to an actuation device engaging therewith. Thus, the drillingfluid passing through the expandable reamer may be temporarily preventedby an actuation device, which may cause the actuation sleeve to bedisplaced by the force generated in response thereto. Sufficientdisplacement of the actuation sleeve may allow drilling fluid tocommunicate with an interior surface of the at least one movable blade,the pressure of the drilling fluid forcing the movable blades to expandlaterally outwardly.

Generally, an expandable reamer may be configured with at least onecutting structure comprising at least one of a PDC cutter, a tungstencarbide compact, and an impregnated cutting structure or any othercutting structure as known in the art. For example, the at least onemovable blade may carry at least one cutting structure comprising a PDCcutter having a reduced roughness surface finish. Further, a pluralityof superabrasive cutters may form a first row of the plurality ofsuperabrasive cutters positioned on the at least one laterally movableblade and may also form at least one backup row of superabrasive cuttersrotationally following the first row of superabrasive cutters andpositioned on the at least one laterally movable blade. Optionally, atleast one of the plurality of superabrasive cutters may be oriented soas to exhibit a substantially planar surface that is orientedsubstantially parallel to the direction of cutting of at least onerotationally preceding superabrasive cutter. Also, at least onedepth-of-cut-limiting feature may be formed upon the expandable reamerso as to rotationally precede at least one of the plurality ofsuperabrasive cutters. In yet a further cutting element-related aspectof the present invention, at least one cutting structure may bepositioned circumferentially following a rotationally leading contactpoint of the at least one laterally movable blade carrying the at leastone cutting structure.

Also, the expandable reamer of the present invention may include atleast one blade-biasing element for returning an at least one laterallymovable blade to its initial unexpanded condition. For instance, theblade-biasing elements may be configured so that only a drilling fluidflow rate exceeding a selected drilling fluid flow rate may cause themovable blades to move laterally outward to their outermost radial orlateral position. Further, a plurality of blade-biasing elements may beprovided for biasing at least one laterally movable blade laterallyinwardly. For example, a first coiled compression spring may bepositioned within a second coiled compression spring. Optionally, thefirst coiled compression spring may be helically wound in an oppositedirection in comparison to the second coiled compression spring.

In another aspect of the present invention, an expandable reamer mayinclude at least one blade-dampening member for limiting a rate at whichthe at least one laterally movable blade may be laterally displaced. Forexample, the at least one blade-dampening member may comprise a viscousdampening member or a frictional dampening member. In another example, adampening member may include a body forming a chamber, the chamberconfigured for holding a fluid. Further, the dampening member may beconfigured for releasing the fluid through an aperture formed inresponse to development of a contact force between the at least onelaterally movable blade and the at least one dampening member.

In addition, the outermost position of the movable blades, whenexpanded, may be adjustable. For instance, the expandable reamer of thepresent invention may be configured so that a spacer element may be usedto determine the outermost lateral position of a movable blade. Such aspacer element may generally comprise a block or pin that may beadjusted or replaced. Alternatively, a spacer element may comprise anannular body disposed about a piston body of the at least one laterallymovable blade.

In a further aspect of the present invention, a piston body of the atleast one laterally moveable blade may be configured to fit within acomplementarily shaped bore formed in the structure for limiting theoutermost lateral position of the at least one laterally movable blade.At least one of the laterally movable blades and the structure forlimiting the outermost lateral position of the at least one laterallymovable blade may be configured for reducing or inhibiting misalignmentof the movable blade in relation to the structure for limiting theoutermost lateral position of the at least one laterally movable blade.Particularly, a piston body of the at least one movable blade maycomprise a generally oval, generally elliptical, tri-lobe, dog-bone, orother arcuate shape as known in the art, and configured for inhibitingmisalignment thereof with respect to an aperture within which it ispositioned. Optionally, a metallic or nonmetallic layer may be depositedupon at least one of the piston body of a movable blade and a boresurface of an aperture within which it is positioned. For instance, anickel layer may be deposited upon at least one of the piston body of amovable blade and a bore surface of an aperture within which it ispositioned. Such a metallic or nonmetallic layer may be deposited by wayof electroless deposition, electroplating, chemical vapor deposition,physical vapor deposition, atomic layer deposition, electrochemicaldeposition, or as otherwise known in the art and may be from about0.0001 inch to about 0.005 inch thick. In one embodiment, an electrolessnickel layer having dispersed TEFLON® particles may be formed upon atleast one of the piston body of a movable blade and a bore surface of anaperture within which the laterally movable blade is positioned.

Further, at least a portion of a blade profile of the at least onelaterally movable blade may be configured for reaming in at least one ofan upward longitudinal direction and a downward longitudinal direction.Also, at least a portion of a blade profile of a movable blade mayexhibit an exponential or other mathematically defined shape (e.g.,radial position varies exponentially as a function of longitudinalposition). Such a configuration may be relatively durable with respectto withstanding reaming of a subterranean formation.

In another exemplary aspect of the present invention, a fluid-filledchamber and at least one intermediate piston element may be configuredso that the pressure developed by the drilling fluid or an externalsource (e.g., a turbine, pump, or mud motor) may be transmitted as aforce to the at least one movable blade. Such a configuration mayprotect the movable assemblies from contaminants, chemicals, or solidswithin the drilling fluid. For instance, it may be desirable to power anexpandable reamer of the present invention by way of a downhole pump orturbine-generated electrical power. Downhole pumps or turbines may allowfor an expandable reamer to be used when the drilling fluid flow ratesand pressures that are required to actuate the tool are not available ordesirable.

One embodiment includes a drilling fluid path for communicating drillingfluid through the expandable reamer without interaction with the atleast one laterally movable blade. Further, the expandable reamer mayinclude an actuation chamber in communication with the at least onelaterally movable blade that is substantially sealed from the drillingfluid path and configured for developing pressure therein for moving theat least one laterally movable blade laterally outwardly.

In another embodiment, an expandable reamer may include at least oneintermediate piston element positioned between a pressure source and theat least one laterally moveable blade and configured for applying alaterally outward force to the at least one laterally moveable blade.

In a further aspect of the present invention, the structure for limitingan outermost lateral position of the at least one laterally movableblade may be affixed to the tubular body by a frangible element.Further, the frangible element may be structured for failing if thelateral position of at least one laterally movable blade exceeds theinnermost lateral position and a selected upward longitudinal force isapplied to the expandable reamer. Such a configuration may provide afail-safe alternative for returning the at least one movable bladelaterally inwardly if the at least one blade-biasing element fails to doso.

Further, the expandable reamer of the present invention may include abearing pad disposed proximate to one end of a movable blade. Thus, inthe direction of drilling/reaming, the bearing pad may longitudinallyprecede or follow the laterally movable blade. Bearing pads may comprisehardfacing material, tungsten carbide, diamond or other superabrasivematerials. More particularly, a lower longitudinal region of a bearingpad may include a plurality of protruding ridges comprisingwear-resistant material.

The expandable reamer of the present invention may include awear-resistant coating deposited upon at least a portion of a surfacethereof. For example, at least a portion of a surface of an expandablereamer may include at least two different hardfacing materialcompositions deposited thereon. Optionally, at least a portion of asurface of the expandable reamer of the present invention may include anadhesion-resistant coating.

Further, the present invention contemplates methods of reaming aborehole in a subterranean formation. Particularly, an expandable reamerapparatus may be disposed within a subterranean formation. Theexpandable reamer apparatus may include a plurality of blades and atleast one laterally movable blade, each blade carrying at least onecutting structure. Also, the at least one laterally movable blade may bebiased to a laterally innermost position corresponding to an initialdiameter of the expandable reamer. Further, a drilling fluid may beflowed through the expandable reamer via a drilling fluid flow pathwhile preventing the drilling fluid from communicating with the at leastone laterally movable blade. Additionally, the drilling fluid may beallowed to communicate with the at least one laterally movable blade byintroducing an actuation device into the expandable reamer apparatus.The at least one laterally movable blade may be to move to an outermostlateral position corresponding to an expanded diameter of the expandablereamer apparatus and a borehole may be reamed in the subterraneanformation by rotation and displacement of the expandable reamerapparatus within the subterranean formation.

Alternatively, an expandable reamer apparatus may be disposed within asubterranean formation, the expandable reamer apparatus including aplurality of blades and having at least laterally movable blade, eachblade carrying at least one cutting structure. Also, the at least onelaterally movable blade may be biased to a laterally innermost positioncorresponding to an initial diameter of the expandable reamer. Further,a drilling fluid may be flowed through the expandable reamer via adrilling fluid flow path while preventing the drilling fluid fromcommunicating with the at least one laterally movable blade. A chamberin communication with an intermediate piston element may be pressurizedto cause the at least one laterally movable blade to move to anoutermost lateral position corresponding to an expanded diameter of theexpandable reamer apparatus. Thus, the at least one laterally movableblade may be made to move to an outermost lateral position correspondingto an expanded diameter of the expandable reamer apparatus and aborehole may be reamed in the subterranean formation by rotation anddisplacement of the expandable reamer apparatus within the subterraneanformation.

Optionally, the at least one movable blade may be caused to movelaterally inwardly in response to applying a selected longitudinal forceto the expandable reamer.

Features from any of the above-mentioned embodiments may be used incombination with one another in accordance with the present invention.In addition, other features and advantages of the present invention willbecome apparent to those of ordinary skill in the art throughconsideration of the ensuing description, the accompanying drawings, andthe appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the advantages of the present invention can be more readily ascertainedfrom the following description of the invention when read in conjunctionwith the accompanying drawings, which illustrate various embodiments ofthe invention and are merely representations not necessarily drawn toscale, wherein:

FIG. 1A is a conceptual side cross-sectional view of an expandablereamer of the present invention in a contracted state;

FIG. 1B is an enlarged, partial conceptual side cross-sectional view ofthe movable blades of the expandable reamer shown in FIG. 1A;

FIG. 1C is an enlarged, partial conceptual side cross-sectional view ofan upper longitudinal region of the expandable reamer shown in FIG. 1A;

FIG. 1D is an enlarged, partial conceptual side cross-sectional view ofa lower longitudinal region of the expandable reamer shown in FIG. 1A;

FIG. 1E is a conceptual side cross-sectional view of the expandablereamer shown in FIG. 1A in an expanded state;

FIG. 1F is a conceptual side cross-sectional view of a retrievableactuation device;

FIGS. 1G and 1H are conceptual side cross-sectional views of anactuation apparatus shown in respective operational states;

FIGS. 1I and 1J are conceptual side cross-sectional views of anotheractuation apparatus shown in respective operational states;

FIG. 1K is an enlarged, partial conceptual side cross-sectional view ofa slotted sleeve for selectively retaining or releasing an actuationdevice;

FIG. 2A is an enlarged, partial cross-sectional view of a movable bladeof an expandable reamer of the present invention including a nestedconfiguration of blade-biasing elements;

FIG. 2B is an enlarged, partial cross-sectional view of a movable bladeof an expandable reamer of the present invention including two blademotion-dampening members;

FIG. 2C is an enlarged, partial cross-sectional view of a dampeningmember as shown in FIG. 2B;

FIG. 2D is an enlarged, partial cross-sectional view of an alternativeembodiment of a dampening member;

FIG. 3A is a conceptual partially cross-sectioned side view of a movableblade of an expandable reamer of the present invention including a fluidaperture proximate thereto;

FIG. 3B is an enlarged partial cross-sectional view of the fluidaperture shown in FIG. 3A;

FIG. 3C is a schematic partially cross-sectioned side view of twomovable blades shown as if they were unrolled from the circumference ofthe drill bit and positioned upon a substantially planar surface;

FIGS. 4A and 4B are conceptual top elevation views of the expandablereamer shown in FIGS. 1A-1E of the present invention in a contractedstate and an expanded state respectively;

FIG. 4C is a cross-sectional bottom elevation view taken through movableblades of an expandable reamer as shown in FIGS. 1A-1E;

FIG. 4D is a partial bottom elevation view of an end region of a movableblade showing cutting element positions thereon;

FIG. 5A is a front view of a movable blade;

FIG. 5B is a side view of the movable blade as shown in FIG. 5A;

FIG. 5C is a back view of the movable blade as shown in FIG. 5A;

FIG. 5D is a cross-sectional view of the movable blade as shown in FIG.5A, taken through the piston body thereof;

FIG. 5E-1 is a cross-sectional view of an alternative embodiment of amovable blade as shown in FIG. 5A, taken through the piston bodythereof;

FIG. 5E-2 is a cross-sectional view of another alternative embodiment ofa moveable blade as shown in FIG. 5A, taken through the piston bodythereof;

FIG. 5F-1 is a perspective view of a movable blade of an expandablereamer according to the present invention;

FIG. 5F-2 is a perspective view of a movable blade of an expandablereamer according to the present invention including a row of backupcutting elements;

FIG. 5G is a conceptual side cross-sectional view of a movable bladeprofile according to the present invention;

FIG. 5H is a conceptual side cross-sectional view of an alternativeembodiment of a moveable blade profile according to the presentinvention;

FIG. 6A is a side cross-sectional view of a retention element;

FIG. 6B is a front view of a retention element as shown in FIG. 6A;

FIG. 6C is a partial cross-sectional back view of the retention elementas shown in FIG. 6A;

FIG. 6D is a top elevation view of the retention element as shown inFIG. 6A;

FIG. 7A is an enlarged, partial cross-sectional view of a movable bladeof an expandable reamer of the present invention including two bladespacer elements;

FIG. 7B is an enlarged, partial cross-sectional view of a movable bladeof an expandable reamer of the present invention including analternative blade spacer element embodiment;

FIG. 7C is an enlarged, partial cross-sectional view of a movable bladeof an expandable reamer of the present invention including a furtheralternative blade spacer element embodiment;

FIG. 7D is a front view of the blade spacer element shown in FIG. 7C;

FIG. 8A is a conceptual side cross-sectional view of an embodiment of anexpandable reamer of the present invention in an expanded state;

FIG. 8B is a conceptual partial side cross-sectional view of anotherembodiment of expandable reamer of the present invention in an expandedstate;

FIG. 8C is an enlarged, partial side cross-sectional view of a movableblade of an expandable reamer of the present invention including afrangible element for preventing or allowing pressurized fluidcommunication therewith;

FIG. 8D is an enlarged, partial side cross-sectional view of a movableblade of an expandable reamer of the present invention including anintermediate piston element having a plurality of protrusions for movingthe movable blade;

FIG. 8E is an enlarged, partial side cross-sectional view of a movableblade of an expandable reamer of the present invention including aplurality of intermediate piston elements for moving the moveable blade;

FIG. 9A is an enlarged, partial side cross-sectional view of a movableblade of an expandable reamer of the present invention affixed within anintermediate element affixed to a tubular body of the expandable reamerby way of a frangible element;

FIG. 9B is an enlarged, partial side cross-sectional view of a movableblade of an expandable reamer of the present invention wherein themovable blade is structured for movement along a direction that isnon-perpendicular to the longitudinal axis of the expandable reamer;

FIG. 10A is an enlarged, partial side cross-sectional view of a portionof an expandable reamer as shown in FIGS. 1A-1E including bearing pads;

FIGS. 10B-10E are views of alternative embodiments of a portion of asurface of a bearing pad as shown in FIG. 10A, taken in accordance withreference line C-C as shown in FIG. 10 a; and

FIGS. 11A and 11B show perspective views of movable blades of anexpandable reamer of the present invention includingdepth-of-cut-limiting surfaces and structures, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to an expandable reamerapparatus for enlarging a subterranean borehole. An expandable reamerapparatus may be advantageous for passing through a bore of a certainsize, expanding to another, larger size, and reaming a subterraneanborehole having the larger size. For instance, an apparatus having atleast one moveable blade may be utilized for passing through a casing orlining disposed within a subterranean borehole and reaming therebelow.

Referring to FIG. 1A of the drawings, a conceptual schematiccross-sectional side view of an expandable reamer 10 of the presentinvention is shown, the side view taken through and viewedperpendicularly to each of movable blades 12 and 14. The expandablereamer 10 may be attached to a drill pipe, casing, liner, or othertubular structure, as known in the art, for communicating fluid thereinand rotating the expandable reamer 10 so as to form a borehole in asubterranean formation. Expandable reamer 10 includes a tubular body 32including an upper tubular body section 32A and a lower tubular bodysection 32B with a bore 31 extending therethrough. As mentioned above,expandable reamer 10 includes movable blades 12 and 14 outwardly spacedfrom the centerline or longitudinal axis 11 of the tubular body 32.However, the present invention is not so limited. Rather, an expandablereamer of the present invention may include at least one movable blade,without limitation. Also, if an expandable reamer includes a pluralityof movable blades, each movable blade of the plurality of movable bladesmay be circumferentially arranged with respect to one another and aboutthe longitudinal axis 11 of expandable reamer 10 as desired, withoutlimitation. Further, each of the plurality of movable blades may bearranged axially along longitudinal axis 11 at different elevations orpositions, as desired, without limitation.

Tubular body 32 includes a male-threaded pin connection 8 at its lowerlongitudinal end as well as a female-threaded box connection 9 at itsupper longitudinal end, as known in the art. As used herein, “upper”refers to a longitudinal position away from an end of expandable reamer10 including male-threaded pin connection 8. Accordingly, as usedherein, “lower” refers to a longitudinal position toward an end ofexpandable reamer 10 including male-threaded pin connection 8. Movableblades 12 and 14 may each carry a plurality of cutting elements, whichare not shown in FIG. 1A for clarity, but are shown in FIG. 1B, asdiscussed hereinbelow.

Particularly, FIG. 1B shows an enlarged view of movable blades 12 and 14of reamer 10 as shown in FIG. 1A. Cutting elements 36 are shown only onmovable blade 12, as the cutting elements (not shown) on movable blade14 would be facing in the direction of rotation of the expandable reamer10 (i.e., away from the viewer) and, therefore, may not be visible onmovable blade 14 in the view depicted in FIG. 1B. Cutting elements 36may comprise PDC cutting elements, thermally stable PDC cutting elements(also known as “TSPs”), superabrasive impregnated cutting elements,tungsten carbide cutting elements, or any other known cutting element ofa material and design suitable for the subterranean formation throughwhich a borehole is to be reamed using expandable reamer 10. Onesuitable superabrasive impregnated cutting element is disclosed in U.S.Pat. No. 6,510,906 to Richert et al., assigned to the assignee of thepresent invention, the disclosure of which is incorporated in itsentirety by reference herein.

Optionally, at least one of cutting elements 36 may comprise a so-called“polished” PDC cutter. For example, U.S. Pat. Nos. 6,145,608 to Lund etal., 5,967,250 to Lund et al., 5,653,300 to Lund et al., and 5,447,208to Lund et al., all assigned to the assignee of the present invention,and the disclosure of each is hereby incorporated in its entirety bythis reference, disclose a PDC cutting element having a reduced surfaceroughness. Such a cutting element may be desirable for reducing frictionwhen engaging a subterranean formation. Of course, any cutting elementfor drilling a subterranean formation, as known in the art, may beemployed upon an expandable reamer of the present invention; withoutlimitation.

In FIG. 1A, the expandable reamer 10 is shown in a contracted state,where the movable blades 12 and 14 are positioned radially or laterallyinwardly. “Laterally,” as used herein, refers to movement of a movableblade generally toward or away from the longitudinal axis 11. Thus, suchmovement may be along a generally radial direction, a non-radialdirection, or even a partially longitudinal direction, withoutlimitation. As shown in FIG. 1A, the outermost lateral extent of movableblades 12 and 14 may substantially coincide with or not exceed the outerdiameter of the tubular body 32. Such a configuration may protectcutting elements 36 (see FIG. 1B) as the expandable reamer 10 isdisposed within a bore that is smaller than the expanded diameter of theexpandable reamer 10. Alternatively, the outermost lateral extent ofmovable blades 12 and 14 may exceed or fall within the outer diameter oftubular body 32.

Bearing pads 34 and 38 may be configured generally for preventingexcessive wear to any of upper tubular body section 32A and lowertubular body section 32B, adjacent to bearing pads 34, 38, respectively.Therefore, bearing pads 34 and 38 may comprise at least one materialresistant to wear, such as, for instance, tungsten carbide, diamond, orcombinations thereof. Accordingly, bearing pads 34 and 38 may be affixedto upper tubular body section 32A by way of removable lock rods (lockrods 106 are shown in FIG. 4C) as described hereinbelow in greaterdetail. In one embodiment, bearing pads 34 and 38 may be removable fromupper tubular body section 32A by way of removing the removable lockrods (not shown). Alternatively, bearing pads 34 and 38 may be affixedto upper tubular section body section 32A and, optionally, removabletherefrom, by way of pins, threaded elements, splines, welding, brazing,dovetail-shaped configurations, combinations thereof, or as otherwiseknown in the art.

As shown in FIG. 1A, the relative position of actuation sleeve 40 inrelation to fixed sleeve 39 may prevent drilling fluid fromcommunicating with movable blades 12 and 14. Generally, at least onesealing element may be positioned between actuation sleeve 40 and fixedsleeve 39 for preventing flow therebetween. In further detail, FIG. 1Cshows an enlarged view of an upper portion of expandable reamer 10,wherein fixed sleeve 39 may be positioned within upper tubular bodysection 32A and retained therein via locking element 37 (e.g., a splitring). Also, as shown in FIG. 1C, actuation sleeve 40 may be affixed tofixed sleeve 39 via at least one retention element 41 (e.g., shear pin).Furthermore, as shown in FIG. 1C, sealing element 43 may be positionedbetween actuation sleeve 40 and fixed sleeve 39. Sealing element 43 maysealingly engage both actuation sleeve 40 and fixed sleeve 39 and may bepositioned within a cavity formed in the actuation sleeve 40 or fixedsleeve 39. Such a configuration may facilitate retention of sealingelement 43 therein in response to disengagement of actuation sleeve 40from fixed sleeve 39, described hereinbelow in greater detail. Thus,sealing element 43 in combination with sealing element 45 maysubstantially prevent or inhibit communication of drilling fluid withmovable blades 12 and 14 in the configuration as shown in FIG. 1C.Rather, in such configuration, drilling fluid supplied to expandablereamer 10 may simply pass through the fixed sleeve 39, through theinterior of actuation sleeve 40 and downwardly through the remainingportion of the expandable reamer 10.

FIG. 1D shows an enlarged view of a lower portion of expandable reamer10. Particularly, actuation sleeve 40 may be positioned within guidesleeve 60 and sealing elements 47 and 53 may be positioned therebetween.Sealing elements 47 and 53 may be positioned above and below apertures70 formed in actuation sleeve 40 so as to effectively contain drillingfluid therebetween as may be communicated from apertures 70. Guidesleeve 60 may include a service access port 66. As shown in FIG. 1D, anupper collet finger flange 59 of guide sleeve 60 may fit into a shoulderfeature 46 of upper tubular body section 32A. Also, guide sleeve 60 mayinclude a plurality of longitudinally extending fingers 73, wherein atleast one of the plurality of longitudinally extending fingers 73includes an interlocking feature 74, which may be configured for atleast partially engaging a complementary interlocking feature of theactuation sleeve 40, shown as annular groove 72, upon the actuationsleeve 40 moving longitudinally downwardly within guide sleeve 60, asdescribed in greater detail hereinbelow. Such an interlockingconfiguration may prevent the actuation sleeve 40 from further movementafter actuation.

In a further aspect of the present invention, a shock-absorbing member48 may be positioned between the actuation sleeve 40 and the portion ofthe guide sleeve 60 with which contact therewith is expected.Shock-absorbing member 48 may be sized and configured for cushioning theactuation sleeve 40 as flange 44 (FIG. 1A) moves longitudinally downwardand proximate to guide sleeve 60. Accordingly, shock-absorbing member 48may be compressed between actuation sleeve 40 and guide sleeve 60.Shock-absorbing member 48 may comprise a flexible or compliant material,such as, for instance, an elastomer or a polymer. In one exemplaryembodiment, shock-absorbing member 48 may comprise a nitrile rubber.Utilizing a shock-absorbing member 48 between the actuation sleeve 40and guide sleeve 60 may reduce or prevent deformation of at least one ofthe actuation sleeve 40 and the guide sleeve 60 that may otherwise occurdue to impact therebetween.

It should be noted that any sealing elements or shock-absorbing membersdisclosed herein that are included within expandable reamer 10 maycomprise any material as known in the art, such as, for instance, apolymer or elastomer. Optionally, a material comprising a sealingelement may be configured for relatively “high temperature” (e.g., about400° Fahrenheit or greater) use. For instance, seals may be comprised ofTEFLON®, polyetheretherketone (“PEEK™”) material, a polymer material, oran elastomer, or may comprise a metal-to-metal seal. Specifically, anysealing element or shock-absorbing member disclosed herein, such asshock-absorbing member 48 and sealing elements 47 and 53, discussedhereinabove, or sealing elements 5 (FIG. 9A), 164, 62A, 62B, 62C, 67A,67B, 67C, 343A, 343B, 345A, 345B, 352, 379, or 383A-383C discussedhereinbelow, or other sealing elements included by an expandable reamerof the present invention may comprise a material configured forrelatively high temperature use.

In a further aspect of the present invention, actuation sleeve 40 mayinclude an actuation cavity 80 configured for capturing an actuationdevice, wherein the actuation device is configured for causing theactuation sleeve 40 to move longitudinally downwardly. For instance,actuation cavity 80 may be configured with a thin sleeve for acceptingand substantially capturing a ball as disclosed in U.S. Pat. No.6,702,020 to Zachman et al. (e.g., FIGS. 4-7 thereof), assigned to theassignee of the present invention, the disclosure of which isincorporated herein in its entirety by this reference.

Summarizing, actuation sleeve 40 may be positioned longitudinally in afirst position and affixed therein, so that movable blades 12 and 14 areeffectively sealed from communication with drilling fluid passingthrough expandable reamer 10. Accordingly, movable blades 12 and 14 maybe positioned inwardly, due to the laterally inward force ofblade-biasing elements 24, 26, 28, and 30, as long as at least oneretention element 41 (FIG. 1C) affixes (shown as extending within holes42A formed within actuation sleeve 40 and holes 42B formed within fixedsleeve 39) actuation sleeve 40 to fixed sleeve 39. However, at least oneretention element 41 may be sized and configured for failing (i.e.,breaking) in response to a downward force exceeding a minimum selectedforce applied to the actuation sleeve 40. Thus, the present inventioncontemplates that an actuation device (e.g., a ball or otherfluid-blockage element) may be deployed within drilling fluid passingthrough expandable reamer 10, becoming captured within the actuationcavity 80 of the actuation sleeve 40, and causing a downward force todevelop thereon of sufficient magnitude to fail the at least oneretention element 41 and force the actuation sleeve 40 longitudinallydownward.

For instance, as shown in FIG. 1E, substantially spherical actuationdevice 50A may be deployed within the drilling fluid passing throughactuation sleeve 40 and may pass into the interior thereof and may becaptured within actuation cavity 80 formed at a lower end thereof.Particularly, substantially spherical actuation device 50A may beconfigured for substantially inhibiting or blocking the flow of drillingfluid through the actuation cavity 80 of the actuation sleeve 40. Inresponse to the substantially spherical actuation device 50Asubstantially inhibiting the flow of drilling fluid through theactuation sleeve 40, pressure may build; thus, a downward force may beproduced upon the actuation sleeve 40. As the drilling fluid force onthe actuation sleeve 40 exceeds a selected force, the at least oneretention element 41 (FIG. 1C) may fail, causing the actuation sleeve 40to move longitudinally downward within guide sleeve 60. For instance,the downward longitudinal force may increase until a release point of atleast one retention element such as, for instance, at least one shearpin or a collet is exceeded. Thus, an actuation device, such assubstantially spherical actuation device 50A may be dropped withinexpandable reamer 10. In turn, the downward longitudinal force generatedby the drilling fluid pressure within the actuation sleeve 40 may causea friable or frictional element to release the actuation sleeve 40 andcause the actuation sleeve 40 to move longitudinally downward to aposition as shown in FIG. 1E. As shown in FIG. 1E, drilling fluidentering expandable reamer 10 may communicate with the movable blades 12and 14, as described hereinbelow in greater detail.

After the actuation sleeve 40 has moved longitudinally to the lowerposition shown in FIG. 1E, drilling fluid flow is established throughexpandable reamer 10 via volume 17, bores 31 and 29, apertures 70, andlower bore areas 78 and 79. In this way, flow may be communicatedthrough expandable reamer 10 with minimal flow restriction, if any. Itshould be further understood that, optionally, lower tubular bodysection 32B may or may not be affixed to upper tubular body section 32A,as desired.

Accordingly, in one aspect of the present invention, at least oneretention element 41 (FIG.1C) may be configured for releasing theactuation sleeve 40 in response to a selected minimum magnitude oflongitudinally downward force applied to the actuation sleeve 40. In oneexample, since each retention element of a plurality of retentionelements effectively adds resistance to movement of the actuation sleeve40, the number of retention elements 41 employed for affixing theactuation sleeve 40 to the fixed sleeve 39 may be selected in relationto a desired minimum longitudinally downward force on the actuationsleeve for releasing the actuation sleeve 40. Alternatively, a breakingstrength of a frangible element such as at least one retention element41 may be adjusted or selected via structuring the at least oneretention element 41 from a suitable material and of a suitable size inrelation to a desired breaking strength thereof. Of course, many otherconfigurations for limiting or failing or otherwise releasing theactuation sleeve 40 of the present invention may be utilized, includingcollets, shear pins, friable elements, frictional engagement, or otherelements of mechanical design as known in the art. For example, aportion of actuation sleeve 40 may be configured for failing andallowing the actuation sleeve 40 to move.

In a further alternative, an actuation device configured for allowingexpandable reamer 10 to expand may be retrievable. Put another way,after dropping a retrievable actuation device within a drill string,which may be ultimately seated within an actuation cavity 80 proximate alower end of actuation sleeve 40, the retrievable actuation device maybe removed therefrom by any process or apparatus as known in the art. Inone example, a wireline may be employed for retrieving a retrievableactuation device comprising a so-called drop dart, as known in the art.For instance, in one embodiment shown in FIG. 1F, retrievable actuationdevice 51 may have a partially hemispherically shaped lower end 56 formating within the actuation cavity 80 of actuation sleeve 40 and anupper end 54 configured for engagement with a retrieval apparatus, suchas a wireline. Of course, the retrievable actuation device 51 may bestructured for movement through a drill string (not shown) andexpandable reamer 10 in an orientation wherein the partiallyhemispherically shaped lower end 56 precedes the upper end 54 inentering the actuation cavity 80. Upper end 54 may comprise a so-called“latch head” structured for engagement with a retrieval device loweredthereon by a wireline, as known in the art. Removing a retrievableactuation device after actuation of the expandable reamer 10 may beadvantageous for allowing a wireline or other tool or device to passthrough the expandable reamer 10.

It should be noted that, as shown in FIG. 1E, expandable reamer 10 willnot automatically expand if drilling fluid communicates with movableblades 12 and 14. Rather, only a sufficient force on movable blades 12and 14 to overcome blade-biasing elements 24, 26, 28, and 30 may causemovable blades 12 and 14 to move laterally outwardly. Explainingfurther, referring to FIG. 1E, the longitudinal position of theactuation sleeve 40 may allow drilling fluid to act upon the innersurfaces 21 and 23 of movable blades 12 and 14, respectively. Inopposition to the force of the drilling fluid upon the inner surfaces 21and 23 of movable blades 12 and 14, blade-biasing elements 24, 26, 28,and 30 may be configured to provide an inward lateral force upon movableblades 12 and 14, respectively. However, drilling fluid acting upon theinner surfaces 21 and 23 may generate a force that exceeds the forceapplied to the movable blades 12 and 14 by way of the blade-biasingelements 24, 26, 28, and 30, and movable blades 12 and 14 may,therefore, move laterally outwardly. Thus, expandable reamer 10 mayexhibit an expanded state as shown in FIG. 1E, wherein movable blades 12and 14 are disposed at their outermost lateral position. Thus, the flowrate of drilling fluid through expandable reamer 10 may be related tothe pressure acting upon the inner surfaces 21 and 23 of movable blades12 and 14; thus, the flow rate of drilling fluid through expandablereamer 10 may be controlled so as to cause the expansion or contractionof movable blades 12 and 14.

Thus, FIG. 1E shows an operational state of expandable reamer 10 whereinactuation sleeve 40 is positioned longitudinally so that drilling fluidflowing through expandable reamer 10 may communicate with and pressurizethe volume 17 formed within the inner surfaces 21 and 23 of movableblades 12 and 14. Such pressurization may force movable blade 12 againstblade-biasing elements 24 and 26 as well as force movable blade 14against blade-biasing elements 28 and 30. Further, a pressure of thedrilling fluid applied to the inner surfaces 21 and 23 may be ofsufficient magnitude to cause movable blade 12 to compress blade-biasingelements 24 and 26 and matingly engage the inner surface of retentionelement 16 as shown in FIG. 1E. Regions 33A, 33B, 35A, and 35B mayinclude longitudinally extending holes for disposing removable lock rods(not shown) for affixing retention elements 16 and 20 to tubular body32, respectively. Likewise, a pressure of the drilling fluid applied tothe inner surfaces 21 and 23 may be of sufficient magnitude to causemovable blade 14 to compress blade-biasing elements 28 and 30 andmatingly engage the inner surface of retention element 20 as shown inFIG. 1E. Of course, movable blades 12 and 14 may also be caused tocontract laterally subsequent to the actuation sleeve 40 beingpositioned as shown in FIG. 1E and lateral expansion of movable blades12 and 14 for reaming. For instance, as the drilling fluid pressuredecreases, blade-biasing elements 24, 26, 28, and 30 may exert a lateralinward force to bias movable blades 12 and 14 laterally inward.

The present invention further contemplates that an actuation device maybe deployed from an apparatus positioned longitudinally above anexpandable reamer of the present invention. For instance, FIGS. 1G and1H show an actuation apparatus 250 (e.g., a so-called ball-dropapparatus) comprising a tubular body 252 having a male connection 255and a female connection 253 for connection within a drill string (notshown). Actuation apparatus 250 may form a portion of a drill string,longitudinally above an expandable reamer (e.g., expandable reamer 10)of the present invention. Actuation apparatus 250 may include a releasesleeve 260 and a sleeve-biasing element 256 extending between shoulder258 and the lower end of release sleeve 260. Substantially sphericalactuation device 50A, as shown in FIG. 1G, may be positioned withinrecess 257 between cap element 254 and release sleeve 260.

Further, during operation, ejection element 262 (e.g., a spring) may beconfigured for propelling substantially spherical actuation device 50Ainto the bore 251 of substantially spherical actuation device 50A inresponse to release sleeve 260 moving longitudinally downward, as shownin FIG. 1H. Release sleeve 260 may be forced longitudinally downward bydrilling fluid passing through bore 251 of actuation apparatus 250 andthrough orifice 263. Accordingly, orifice 263 may be sized andconfigured in relation to the behavior of sleeve-biasing element 256 sothat a selected drilling fluid flowing through orifice 263 at a minimumselected flow rate (or greater flow rate) may cause longitudinaldisplacement of release sleeve 260 sufficient for allowing thesubstantially spherical actuation device 50A to exit recess 257. Ofcourse, as mentioned above, ejection element 262 may force substantiallyspherical actuation device 50A from within recess 257 and into the bore251 of actuation apparatus 250 as release sleeve 260 moveslongitudinally downwardly to a position as shown in FIG. 1H, asillustrated by the arrows and outline representations of substantiallyspherical actuation device 50A. At least one of ejection element 262 andrecess 257 may be configured for retaining the ejection element 262within recess 257.

As a further alternative, an actuation device may be released by anapparatus of similarity to apparatuses disclosed in U.S. Pat. No.5,230,390 to Zastresek, assigned to the assignee of the presentinvention, and the disclosure of which is incorporated herein in itsentirety by this reference. For example, as shown in FIGS. 1I and 1J, anactuation apparatus 270 may include a release element 282 comprising asleeve having inwardly radially extending features 286 (e.g., forming acollet or collet-like structure) for retaining a substantially sphericalactuation device 50A against a downward longitudinal force. A downwardlongitudinal force may be generated upon substantially sphericalactuation device 50A by drilling fluid moving longitudinally downwardwithin bore 251 of tubular body 252 and past substantially sphericalactuation device 50A through aperture 284 formed in release element 282.If a sufficient force is developed upon substantially sphericalactuation device 50A, actuation device 50A may be forced throughinwardly radially extending features 286 and released from releaseelement 282, traveling longitudinally downwardly through bore 251, asshown in FIG. 1J.

In a further alternative, as shown in FIG. 1K, the lower end ofactuation cavity 80 may be structured with slots 288 (i.e., as a slottedsleeve) to allow fluid to flow around the substantially sphericalactuation device 50A and through exit aperture 295. Resilient annularelements 290, 292 may be secured to the interior of the actuation cavity80, thus retaining the substantially spherical actuation device 50Atherebetween. The resilient annular elements 290, 292 may comprise anyflexible material configured for retaining the substantially sphericalactuation device 50A above the seat 294 under selected drilling fluidflow conditions (e.g., for a selected range of drilling fluid flowrates), but will flex under increased fluid pressure to allow theactuation device 50A to drop. One exemplary embodiment for the resilientannular elements 290, 292 may comprise an annular spring washer, asnap-ring sized to retain the substantially spherical actuation device50A in place, an O-ring, and a spring clip. A conventional resettingtool may be used to retrieve and reset the substantially sphericalactuation device 50A between the resilient annular elements 290, 292 asrequired by the particular drilling conditions.

In another aspect of the present invention, optionally, a so-called“bypass sub” may be assembled within a drill string that includes anexpandable reamer of the present invention. More specifically, a bypasssub may be structured so that if the expandable reamer becomes unable topass drilling fluid therethrough, ports within the bypass sub will openand allow drilling fluid (or another fluid) circulation at least to thelongitudinal position of the bypass sub. Such a configuration mayprovide a mechanism to retain fluid circulation capability along asubstantial portion of a drill string in the event that a deleteriousevent prevents flow through an expandable reamer of the presentinvention.

It may be further appreciated that actuation sleeve 40, fixed sleeve 39,and guide sleeve 60 may be omitted from the bore 31 of expandable reamer10. Accordingly, bore 31 may comprise an open bore extending throughupper and lower tubular body sections 32A and 32B. However, protectionelements (not shown), such as covers may be positioned within bore 31for preventing wear to threads or other features within the bore 31 ofexpandable reamer 10. In such a configuration, drilling fluid willconstantly act against the movable blades 12 and 14. Accordingly,blade-biasing elements 24, 26, 28, and 30 may be configured forsubstantially biasing or holding movable blades 12 and 14 laterallyinwardly for drilling fluid flow rates (which relate to pressures ofdrilling fluid acting on movable blades 12 and 14) that may be desirablewithout expanding movable blades 12 and 14 laterally outwardly forreaming.

Turning to aspects related to at least one movable blade of anexpandable reamer of the present invention, with respect to ablade-biasing element (e.g., any of blade-biasing elements 24, 26, 28,and 30 as shown in FIGS. 1A, 1B, and 1E), the present inventioncontemplates many alternatives. For instance, a blade-biasing elementmay comprise at least one of a Belleville spring, a wave spring, awasher-type spring, a leaf spring, and a coil spring (e.g., comprisingsquare wire, cylindrical wire, or otherwise shaped wire). Further, ablade-biasing element may comprise any material having a suitablestrength and desired elasticity. For instance, in one embodiment, atleast one of blade-biasing elements 24, 26, 28, and 30, as shown in FIG.1A, may comprise at least one of steel, music wire, and titanium.However, the present invention contemplates that any material with arelatively high modulus of elasticity may be utilized for forming ablade-biasing element, without limitation.

In another aspect of the present invention, a plurality of blade-biasingelements may be arranged in a so-called “nested” configuration forbiasing a portion of a movable blade. Particularly, as shown in FIG. 2A,blade-biasing elements 24A and 24B may be positioned within one anotherand within an upper end of retention element 16 for biasing movableblade 12. Also, blade-biasing elements 26A and 26B may be positionedwithin one another and within a lower end of retention element 16 forbiasing movable blade 12. Such an arrangement may provide additionalforce for returning movable blade 12 toward the center of the expandablereamer 10 compared to blade-biasing element 26A alone. Further, each ofblade-biasing elements 24A and 24B may be wound in opposite helicaldirections. Such a configuration may inhibit interference (e.g., coilsof one of the blade-biasing elements 24A and 24B becoming interposedbetween coils of the other of the blade-biasing elements 24A and 24B)between the blade-biasing elements 24A and 24B.

Optionally, in another aspect of the present invention related to amovable blade, at least one dampening member (e.g., a viscous damper orfrictional damper) may be configured for limiting a rate of laterallyoutward displacement of at least one movable blade of an expandablereamer. For instance, FIG. 2B shows an enlarged side cross-sectionalview of movable blade 12 wherein dampening members 90 are positionedproximate each of the longitudinal ends of movable blade 12, betweenretention element 16 and movable blade 12. Dampening members 90 may bepositioned within an interior or proximate (e.g., alongside)blade-biasing elements (blade-biasing elements 24 and 26 as shown inFIGS. 1A, 1B and 1E are not shown in FIG. 2B, for clarity) positionedbetween movable blade 12 and retention element 16. More specifically, asshown in FIG. 2C, which shows an enlarged view of a region of expandablereamer 10 proximate the upper end of movable blade 12, dampening member90 may comprise a body 97 having a crushable region 92, the body 97 alsoattached to a cap 98 having a bellows 96 and a movable element 95. Body97, in combination with cap 98, bellows 96, and movable element 95,define a chamber 94 of dampening member 90. Bellows 96 and movableelement 95 may be configured for substantially equalizing the pressurebetween the chamber 94 and a pressure exterior thereto (e.g., pressureof drilling fluid). Such a structure may be known as a “compensator.”Chamber 94 may be filled with a fluid, such as, for instance, oil,water, or another fluid. Further, dampening member 90 may include afrangible port 93 that is structured for failing or otherwise allowingfluid within chamber 94 of dampening member 90 to be expelled or passedtherethrough in response to movable blade 12 matingly engaging andcrushing crushable region 92.

Thus, during operation, as movable blade 12 is forced toward retentionelement 16, movable element 95 may be forced against cap 98. Thus, acontact force may be developed between the movable blade 12 and thedampening member 90. In turn, pressure may build within chamber 94 to amagnitude sufficient, by way of crushing of crushable region 92, so asto fail frangible port 93 and cause fluid to be expelled from thechamber 94. Accordingly, the relative speed at which movable blade 12may move toward retention element 16 may be tempered or limited by therelationship between the pressure within the chamber 94 and the rate atwhich fluid is expelled from the frangible port 93. Optionally,crushable region 92 may be structured for collapsing into an interior(i.e., chamber 94) of body 97 of dampening member 90. Such aconfiguration may be advantageous for avoiding interference with ablade-biasing element (not shown) proximate to the dampening member 90.

Alternatively, as shown in FIG. 2D, which shows a schematic sidecross-sectional view of movable blade 12, a dampening member 91 maycomprise a body 101 forming a chamber 102 substantially filled with afluid (e.g., oil, water, etc.) and having at least one frangible orpreferentially weakened port 99. Dampening members 91 may be positionedwithin an interior or proximate (e.g., alongside) blade-biasing elements(blade-biasing elements 24 and 26 as shown in FIGS. 1A, 1B and 1E arenot shown in FIG. 2D, for clarity) positioned between each of thelongitudinal ends of movable blade 12. Such a configuration may cause,subsequent to a selected contact force between the movable blade 12 andthe dampening member 91 and during movement of movable blade 12laterally outwardly, the fluid within chamber 102 of body 101 to beexpelled therefrom. Thus, the size of the at least one port 99, as wellas the properties of the fluid (e.g., viscosity, density, etc.), maysubstantially limit the rate at which the fluid may be expelledtherefrom. In turn, movable blade 12 may be displaced laterallyoutwardly at a substantially limited rate in relation to the rate atwhich fluid is expelled from the at least one port 99. Of course, thebody 101 may be substantially crushed or compressed as the movable blade12 is displaced toward retention element 16 and may also be structuredtherefor. Further, dampening member 91 may be structured for avoidinginterference with a blade-biasing element proximate to the dampeningmember 90. Thus, dampening member 91 may not substantially influencepositioning of movable blade 12 against retention element 16, other thanlimiting a lateral speed of movable blade 12 toward retention element16.

In a further aspect of the present invention, an aperture or portconfigured for conducting drilling fluid for facilitating cleaning ofthe formation cuttings from the cutting elements 36 affixed to at leastone movable blade of the expandable reamer during reaming. In oneembodiment, as shown in FIGS. 3A and 3B, an aperture 166 may extend fromthe bore 31 of upper tubular body section 32A to an exterior surfacethereof, structured for delivering drilling fluid in a directiongenerally toward cutting elements 36 on a movable blade 12. Aperture 166may include an oversized inlet region 165 and a threaded surface 163 formating with a nozzle 160 configured for communicating fluid from aninterior of the upper tubular body section 32A to an exterior surfacethereof. The interior of the upper tubular body section 32A adjacent tothe nozzle 160 may also be counterbored or recessed around an inlet tonozzle 160 for the purpose of preventing erosion to upper tubular bodysection 32A. Nozzle 160 may also include a groove for carrying a sealingelement 164 positioned between the upper tubular body section 32A andthe nozzle 160. Further, aperture 166 may be oriented at an angle towardthe upper or lower longitudinal end of the expandable reamer 10.Alternatively, an aperture 166 may be installed in the horizontaldirection, (i.e., substantially perpendicular to a longitudinal axis)through tubular body 32 of the expandable reamer 10. Of course, thepresent invention contemplates that an aperture 166 may be oriented asdesired. Other configurations for communicating fluid from the interiorof the tubular body 32 to the cutting elements 36 carried by a movableblade are contemplated, including a plurality of apertures proximate orextending through at least one movable blade of expandable reamer 10.Alternatively, at least one of movable blades (e.g., movable blade 12,movable blade 14, or other movable blades) of the expandable reamer 10may be configured with an aperture 166, as described above, extendingtherethrough.

In a further aspect of the present invention related to drilling fluid,it may be advantageous to configure the space between the movable bladesof an expandable reamer for facilitating nozzle placement and drillingfluid flow. Explaining further, a (circumferential) gap or space betweenblades of a drill bit or a reamer is commonly termed a “junk slot.”According to the present invention, a junk slot defined between twomovable blades of an expandable reamer may be tapered or exhibit avarying size so that an area or width (shown in FIG. 3C as “w”) betweenthe movable blades increases or decreases along a longitudinaldirection. Alternatively, a size (e.g., an area or width) of a junk slotbetween the movable blades may, be stepped or otherwise sequentiallyvary (i.e., increase or decrease or vice versa) in the direction ofdrilling fluid flow.

In one example, as shown in FIG. 3C, movable blades 12 and 14 are shownin a partially cross-sectioned side view, as if they were unrolled fromthe circumference of the drill bit and positioned upon a substantiallyplanar surface. Such a view is merely a representation to betterillustrate the longitudinal geometry of junk slot 82 (also shown inFIGS. 4A and 4B). Particularly, junk slot 82 may be defined betweenblade bases 85A and 85B (also shown in FIGS. 4A and 4B), as well asmovable blades 12 and 14. (As shown in FIG. 4C, blade bases 85A and 85Bmay be circumferential extensions of tubular body 32 (not shown).)Further, as shown in FIG. 3C, blade bases 85A and 85B may be shapedlongitudinally so as to form a junk slot 82 that exhibits a generallydecreasing size or area as a function of an upwardly increasinglongitudinal position. Such a configuration may provide additionalcapability for placement of at least one nozzle 160 proximate the lowerlongitudinal end of movable blades 12 and 14 and may promote desirableflow characteristics of drilling fluid therefrom.

An expandable reamer according to the present invention may include atleast one movable blade or, alternatively, a plurality of movableblades. In addition, if a plurality of movable blades is carried by anexpandable reamer, the plurality of movable blades may be symmetricallycircumferentially arranged about a longitudinal axis of the expandablereamer or, alternatively, nonsymmetrically circumferentially arrangedabout a longitudinal axis of the expandable reamer.

For completeness, FIGS. 4A-4C each show a conceptual top elevation viewof one embodiment of expandable reamer 10, wherein expandable reamer 10includes symmetrically circumferentially arranged blade bases 85A-85Cincluding movable blades 12, 13, and 14 therein. Further, movable blades12, 13, and 14 of expandable reamer 10 may be caused to expand from alaterally innermost position corresponding to boundary circle 7A to anoutermost lateral position defined by boundary circle 7B and theborehole may be enlarged by the combination of rotation and longitudinaldisplacement of the expandable reamer 10. Accordingly, each movableblade 12 of an expandable reamer may be positioned circumferentially asdesired in relation to one another. Also, FIG. 4B illustrates that eachof the side cross-sectional views as shown in FIGS. 1A-1E may be takenalong reference line A-A, comprising two line segments extending fromlongitudinal axis 11, the side cross-sectional views as are shown inFIGS. 1A-1E being substantially perpendicular to each line segment ofreference line A-A.

Also, as shown in FIGS. 4A-4C, movable blades 12, 13, and 14 may beretained within expandable reamer 10 by removable lock rods 106extending longitudinally along the upper tubular body section 32A of theexpandable reamer 10 on sides of movable blade 12, 13, and 14,respectively. Additionally, as shown in FIG. 4C, removable lock rods 106may at least partially extend along recesses 159 formed in retentionelements 16, 20, and 49 and proximately positioned cooperatively shapedrecesses 105 formed in upper tubular body section 32A. Further, each oflock rods 106 may be captured or otherwise affixed at longitudinal upperand lower ends (not shown) thereof within a hole (not shown) extendinginto upper tubular body section 32A substantially aligned therewith. Ofcourse, lock rods 106 may be affixed to upper tubular body section 32Aby welding, splines, pins, combinations thereof, or otherwise affixinglock rods 106 thereto. Alternatively, lock rods 106 may be positionedwithin holes formed within upper tubular body section 32A and aremovable plug (threaded, pinned, or otherwise affixed to upper tubularbody section 32A) may be placed within an end of at least one of theholes. Thus, affixing both longitudinal ends of lock rods 106 to uppertubular body section 32A also affixes, by extending longitudinally alongthe exterior within recesses 105 and 159, retention element 16 to uppertubular body section 32A and movable blades 12, 14, and 13 therein. Putanother way, recesses 105 and 159 formed in the retention elements 16,20, and 49 and upper tubular body 32A, respectively, and extensions ofsuch recesses (formed as holes) into upper tubular body 32A in theregions 33A, 33B, 35A, and 35B, as shown in FIGS. 1A-1C, may allow forremovable lock rods 106 to be inserted therethrough, extending betweenretention elements 16, 20, and 49 and upper tubular body section 32A,thus affixing retention elements 16, 20, and 49 to upper tubular body32A. When fully installed, removable lock rods 106 may extendsubstantially the length of retention elements 16, 20, and 49,respectively, but may extend further, depending on how the removablelock rods 106 are affixed to the upper tubular body 32A. Of course,optionally, removable lock rods 106 may be detached from the uppertubular body section 32A to allow for removal of retention elements 16,20, and 49 as well as movable blades 12, 14, and 13, respectively,therefrom. Accordingly, the present invention contemplates that aretention element 16, 20, or 49, a movable blade 12, 14, or 13 or both,of expandable reamer 10 may be removed, replaced, or repaired by way ofremoving the removable lock rods 106 from the recesses 105 and 159formed in retention elements 16, 20, and 49 and upper tubular bodysection 32A, respectively. Of course, many alternative removableretention configurations are possible including pinned elements,threaded elements, dovetail elements, or other connection elements knownin the art to retain a movable blade. Also depicted in FIG. 4C areperipheral sealing elements 67A, 67B, 67C, 62A, 62B, and 62C carried inrespective grooves formed into the exterior of blades 12, 14, and 13,and retention elements 16, 20, and 49, respectively, which may beconfigured for preventing debris and contaminants from the wellbore fromentering the interior of expandable reamer 10 and may also maintain arelatively higher pressure within the expandable reamer 10, as comparedto a pressure experienced upon an exterior of the expandable reamer 10.

The present invention also contemplates that cutting elements 36 may bepositioned on a movable blade of the expandable reamer 10 so as to becircumferentially and rotationally offset from an outer, rotationallyleading edge portion of a movable blade where a rotationally leadingcontact point is likely to occur. Such positioning of the cuttingelements rotationally, or circumferentially, to a position rotationallyfollowing the casing contact point located on the radially outermostleading edge of a movable blade may allow the cutters to remain onproper drill diameter for enlarging the borehole, but are, in effect,recessed or protected from the rotationally leading contact point. Suchan arrangement is disclosed and claimed in U.S. Pat. No. 6,695,080 toPresley et al., assigned to the assignee of the present invention, thedisclosure of which is incorporated herein in its entirety by thisreference.

In further detail, FIG. 4D illustrates a top elevation view of a radialend region 14E of movable blade 14 having cutting elements 36 disposedthereon. The radial end region 14E of movable blade 14 may includehardfacing H extending out to reaming diameter R (also showing directionof reaming). Thus, hardfacing H may provide a bearing surface for thegage while a formation is being reamed. In addition, the hardfacing Hmay protect the cutting elements 36, which are circumferentially rotatedtoward the back of movable blade 14 and away from initialcircumferential contact point C. Such a configuration may substantiallyinhibit contact between the cutting elements 36 and a formation, acasing, or another stricture to be reamed. In addition, superabrasive,specifically diamond inserts (e.g., hemispherical superabrasive inserts,BRUTE™ PDC elements, etc.), may be appropriately placed proximatecutting elements 36. Such a configuration may provide additionalprotection for cutting elements 36.

For further exploring aspects of the present invention, a movable bladeis described in additional detail as follows. Specifically, FIGS. 5A-5Cshow movable blade 12, 14 as shown in FIGS. 1A, 1B, and 1E. FIG. 5Ashows a side front view of movable blade 12, 14, wherein the cuttingelements (not shown) facing toward the viewer (i.e., positioned as blade12 is positioned in FIG. 1B). Movable blade 12, 14 includes cuttingelement pockets 132 disposed along a so-called profile 128, as discussedin more detail hereinbelow. FIG. 5B shows a side view of movable blade12, 14 and shows depressions 130A and 130B, which may be configured forengaging and facilitating positioning of an end of a blade-biasingelement (not shown) engaged therewith, as shown in FIGS. 1A and 1E. FIG.5C shows a side back view of movable blade 12, 14, wherein the cuttingelements (not shown) face away from the viewer (i.e., positioned asblade 14 is positioned in FIG. 1B). Movable blade 12, 14 may furtherinclude a base plate 120, a piston body 122 extending therefrom, agroove 126 and cutting element pockets 132 sized and configured forplacement of cutting elements (not shown) therein. Further, a taperedshoulder periphery 124 may extend about the periphery of the movableblade 12, 14. Angle θ between axis X to axis Z is discussed in furtherdetail hereinbelow.

FIG. 5D shows a cross-sectional view taken through piston body 122. Asshown in FIG. 5D, piston body 122 may exhibit a so-called “dog-bone”geometry. Particularly, a cross-sectional shape of the piston body 122may comprise two enlarged ends 138 connected to one another via asubstantially constant body 131 portion of relatively smaller dimensionextending therebetween.

In another embodiment, a movable blade 12, 14 may be configured as shownin FIGS. 5A and 5C, but may have a substantially oval or ellipticalcross-section as shown in FIG. 5E-1 (as opposed to FIG. 5D). Further,the cross-section of a movable blade 12, 14 need not be symmetrical or,alternatively, may be symmetrical if desired. In yet a further example,advantages of which are described in greater detail hereinbelow, amovable blade 12, 14 may have a so-called “tri-lobe” cross-section asshown in 5E-2. Particularly, “tri-lobe” refers to a cross section ofpiston body 122 comprising three alternating enlarged regions 141A,141B, and 141C, separated by necked regions 143A and 143B, as shown inFIG. 5E-2.

FIG. 5F-1 shows a movable blade 12 having a generally oval piston body122, as shown in FIG. 5E-1, in a perspective view. As a furthercontemplation of the present invention, a movable blade may includeso-called “BRUTE™” PDC cutters. Such BRUTE™ PDC cutters are described inU.S. Pat. No. 6,408,958 to Isbell, et al., assigned to the assignee ofthe present invention, the disclosure of which is incorporated herein inits entirety by this reference, which discloses a cutting assembly thatmay be employed upon an expandable reamer of the present invention. Morespecifically, an expandable reamer of the present invention may includea cutting assembly comprised of first and second superabrasive cuttingelements including at least one rotationally leading cutting elementhaving a cutting face oriented generally in a direction of intendedrotation of a bit on which the assembly is mounted to cut a subterraneanformation with a cutting edge at an outer periphery of the cutting face,and a rotationally trailing cutting element oriented substantiallytransverse to the direction of intended bit rotation and including arelatively thick superabrasive table configured to cut the formationwith a cutting edge located between a beveled surface at the side of thesuperabrasive table and an end face thereof.

For example, as shown in FIGS. 5F-1, cutting elements 136 may bepositioned so as to exhibit a substantially planar surface that isoriented substantially parallel to the direction of cutting ofrotationally preceding cutting elements 36. Such a configuration may beadvantageous for limiting the depth of cut of the rotationally precedingcutting elements 36. Cutting elements 136 are shown as being positionedwithin a gage region of movable blade 12, which may be advantageous formaintaining the overall diameter of an expandable reamer during use.However, the present invention contemplates that cutting elements 136may be positioned upon a movable blade or generally upon an expandablereamer of the present invention as desired for resisting wear, limitingengagement (e.g., depth of cut) with a subterranean formation, or both.

Optionally, a so-called “backup” row of cutting elements may bepositioned upon a movable blade rotationally following a leading row ofcutting elements positioned thereon. For example, FIGS. 5F-2 shows aperspective view of movable blade 12 as shown in FIGS. 5F-1, butincluding cutting elements 36B, which are arranged in a backup rowrotationally following cutting elements 36. Cutting elements 36B may besized and positioned in any manner desired, as known in the art.Further, although the row of cutting elements 36B is shown as exhibitingsubstantially similar size and configuration in relation to the row ofcutting elements 36, the present invention contemplates that a backuprow of cutting elements may be employed as desired, without limitation.Put another way, a backup row may comprise at least one cutting elementgenerally rotationally following at least one cutting element. Ofcourse, generally rotationally following at least one cutting elementmay be generally aligned with a preceding cutting element or may bemisaligned with respect thereto, without limitation. Such aconfiguration may provide additional available cutting elementfunctionality (e.g., coverage, material, force balancing, or redundancy)as compared to cutting elements 36 alone.

With respect to a movable blade configuration, it should be understoodthat, generally, an expandable reamer of the present invention may beoperated so as to ream a subterranean formation or other structure in atleast one of a longitudinally upward and downward direction (i.e., alsoknown as “up-drilling,” “up-reaming,” or “down-reaming”). Accordingly,it may be desirable to configure the profile of a movable bladeaccordingly. As used herein, “profile” refers generally to a referenceline upon which each of the cutting elements is placed or lie.Generally, a blade profile may follow an outer lateral outline or bladeshape. For instance, as shown in FIG. 5G, movable blade 12 may includethree profile regions 152, 154, and 158. Such a configuration may bedesirable for predominantly reaming with profile region 158 in alongitudinally downward direction. Profile region 158 may generallyexhibit a parabolic or exponential (e.g., radial position as a functionof longitudinal position) shape. Such a configuration may be relativelydurable with respect to withstanding reaming of a subterraneanformation. Of course, the present invention contemplates that anygeometry (linear, angled, arcuate, etc.) may be selected for any ofprofile regions 152, 154, and 158, without limitation. Profile region154 is also known as a gage region, which corresponds (upon expansion ofmovable blade 12) with an outermost diameter of the expandable reamer.Further, profile region 152, shown as being angled or tapered (e.g.,oriented at 20° or another angle greater or less than 20°, withoutlimitation) with respect to a longitudinal axis of an expandable reamer,may be configured with cutting elements (not shown) for up-drilling orup-reaming (i.e., reaming in an upward longitudinal direction). Also,profile region 152 may facilitate movable blade 12 returning laterallyinwardly during tripping out of a subterranean borehole. Specifically,impacts between the borehole and the profile region 152 may tend to movethe movable blade 12 laterally inward.

Alternatively, as shown in FIG. 5H, movable blade 12 may include profileregions 158A, 154, and 158B. As described hereinabove, profile region154 may comprise a gage region, which corresponds (upon expansion ofmovable blade 12) with an outermost diameter of the expandable reamer.Profile regions 158A and 158B may generally follow a parabolic orexponential (e.g., radial position as a function of longitudinalposition) shape, which may be relatively durable with respect towithstanding reaming of a subterranean formation. Of course, therelative size and shape of the collective profile of a movable blade ofan expandable reamer of the present invention may be selected forfacilitating forming a borehole in at least one of a longitudinallyupward and downward direction and through an anticipated subterraneanformation, as known in the art. For example, as may be appreciated bythe foregoing discussion, an expandable reamer of the present inventionmay be positioned (in a contracted state or condition) within aborehole, expanded and operated so as to ream a subterranean borehole inan upward or downward longitudinal direction, contracted, and removedfrom the reamed subterranean borehole.

In one example, for instance, an exponential shape of a movable bladeprofile may be determined by the following equation:L=a·e ^(r−b)wherein:L is a longitudinal position along a blade profile;e is the base of natural logarithms;a is a constant;b is a constant; andr is a radial position along the blade profile.

Such a blade shape may be advantageous for protecting cutting elementson an expandable reamer from damage during transitions betweensubterranean formations having different properties. Particularly, inone example, at least a portion of profile regions 158, 158A, or 158B asshown in FIG. 5G or 5H may exhibit a shape determined substantially bythe above exponential equation. Explaining further, for example, atleast a portion of profile region 158A may exhibit a shape determined bythe above equation, but inverted (i.e., substitute “−a” for “a” in theabove equation). Particularly, a longitudinally lowermost region ofprofile region 158 may be substantially parabolic to the longitudinalaxis (e.g., longitudinal axis 11, as shown in FIG. 1A). Such aconfiguration may be advantageous, because the portion of the profileregion 158 that is substantially parabolic to the longitudinal axis mayreduce cutting element damage of the expandable reamer as the expandablereamer reams into a relatively harder subterranean formation from arelatively softer formation. Thus, such a configuration may beadvantageous for inhibiting cutting element damage that may occur when asubterranean formation changes (e.g., drilling into a relatively hardersubterranean formation from a relatively softer subterranean formation).

For purposes of further exploring aspects of the present invention, aretention element is described in additional detail as follows.Retention element 16, 20 is shown in FIGS. 6A-6D and may includerecesses 140 and 142 and aperture 150, which forms bore surface 146 fora movable blade to move within as a piston element (i.e., piston body122 of movable blade 12, 14 as shown in FIGS. 5A and 5C). Also, FIG. 6Dshows a top elevation view of retention element 16, 20, depicting groove149 for accepting a sealing element (62A, 62B, and 62C as shown in FIG.4C) and recesses 159 for positioning of lock rods (e.g., lock rods 106as shown in FIG. 4C) therein. End regions 153B and neck regions 152B ofretention element 16, 20, are identified as general regions of contactbetween a movable blade disposed within aperture 150 due to misalignmentbetween the piston body 122 and the aperture 150. Put another way, apiston body 122 of a movable blade 12, 14 may exhibit a substantiallyconstant cross section with respect to its direction of movement withinan aperture 150 having a substantially constant cross section withrespect to the direction of movement of the movable blade 12, 14.Misalignment of the piston body 122 with respect to aperture 150 refersto a nonparallel relationship between the direction of movement of thepiston body 122 of the movable blade 12, 14 and an aperture 150 withinwhich it is positioned. Such misalignment may be caused, at least inpart, by forces applied to a movable blade during drilling or reaming ofa subterranean formation therewith.

Accordingly, in a further aspect of the present invention, at least oneof movable blade 12, 14 and retention element 16, 20 may be configuredfor reducing or inhibiting misalignment of movable blade 12, 14 inrelation to aperture 150 of retention element 16, 20 during movementthereof. Particularly, as may be seen in FIG. 5D, which shows across-sectional view taken through piston body 122, the cross-sectionalshape of the piston body 122 may comprise two enlarged ends 138connected to one another via a substantially constant body 131 portionof smaller dimension extending therebetween. Such a shape may inhibitbinding of the piston body 122 as it moves laterally inwardly andoutwardly during use. Particularly, tipping or rotation of movable blade12, 14, as shown in FIG. 5A and denoted by θ (from axis X to axis Z),may cause regions 152A and 153A to contact retention element 16 (FIGS.1A and 5D). Thus, the piston body of a movable blade may bepreferentially shaped to increase the contact area with a retentionelement in response to tilting or rotation of the movable blade. Thus,each longitudinal side of a movable blade may comprise a generally oval,generally elliptical, tri-lobe, dog-bone, or other arcuate shape asknown in the art, and configured for inhibiting misalignment of a pistonbody of a movable blade with respect to an aperture of a retentionelement within which it is positioned.

Furthermore, at least one of the piston body 122 of a movable blade 12,14 and a bore surface 146 (FIGS. 6A-6C) of retention element 16, 20 maybe structured (e.g., treated or coated) so as to reduce or inhibit wear,localized welding or galling, or other impediments (e.g., friction) torelative motion between piston body 122 and the aperture 150. Forexample, a nickel layer may be deposited upon at least one of the pistonbody 122 of a movable blade and a bore surface 146 of retention element16, 20. Such a nickel layer may be deposited by way of electrolessdeposition, electroplating, chemical vapor deposition, physical vapordeposition, atomic layer deposition, electrochemical deposition, or asotherwise known in the art and may be from about 0.0001 inch to about0.005 inch or more thick. In one embodiment, an electroless nickel layerhaving dispersed TEFLON® particles may be formed upon at least one ofthe piston body 122 of a movable blade 12, 14 and a bore surface 146 ofretention element 16, 20. Such an electroless nickel layer and coatingprocess may be commercially available from TWR Service Corporation ofSchaumburg, Ill. Alternatively, other non-stick low friction materialsand processes are possible. Other relatively hard coatings such as, forinstance, ceramic, nitride, tungsten carbide, diamond, combinationsthereof, or as otherwise known in the art may be formed upon at leastone of the piston body 122 of a movable blade 12, 14 and a bore surface146 of retention element 16, 20, without limitation.

In another aspect of the present invention, the outermost lateralposition of at least one movable blade of an expandable reamer of thepresent invention may be configured to be selectable. Put another way,at least one movable blade may be positioned at a selectable oradjustable radially outermost position by way of at least one spacerelement. Thus, an expandable reamer of the present invention may beadjustable in its reaming diameter. Such a configuration may beadvantageous to reduce inventory and machining costs, and forflexibility in use of an expandable reamer.

In one embodiment, FIG. 7A shows spacer elements 210 positioned betweenretention element 16 and movable blade 12. More specifically, forexample, length “L” as shown in FIG. 7A may be selected so that theoutermost radial or lateral position of movable blade 12 may be adjustedaccordingly when movable blade 12 abuts thereagainst. Spacer elements210 may be disposed within blade-biasing elements 24 and 26,respectively, as shown in FIG. 7A, may be affixed to movable blade 12 orretention element 16 or, alternatively, may freely move therein. Thus,utilizing adjustable spacer elements 210 may allow for a particularmovable blade to be employed in various borehole sizes and applications.For instance, the expandable reamer of the present invention includingadjustable spacer elements may enlarge a particular section of boreholeto a first diameter, then may be removed from the borehole and anotherset of adjustable spacer elements having a different length “L” mayreplace adjustable spacer elements, then the expandable reamer may beused to enlarge another section of borehole at a second diameter.Further, minor adjustment of the outermost lateral position of themovable blade 12 may be desirable during drilling operations by way ofthreads or other adjustment mechanisms when adjustable spacer elements210 may be affixed to either of the movable blade 12 or retentionelement 16.

In another embodiment, FIG. 7B shows spacing element 220, which isconfigured as a continuous band fitting about the periphery of movableblade 12 (i.e., about piston body 122 as shown in FIG. 5A, forinstance). Accordingly, thickness “t” of spacing element 220 may beselected so that the outermost radial or lateral position of movableblade 12 may be adjusted accordingly when spacing element 220 abutsagainst both movable blade 12 and retention element 16. Such aconfiguration may be advantageous for ease of installation andmanufacturing. In yet a further embodiment, FIGS. 7C and 7D show thatspacing element 230 may exhibit a contact area 236 that substantiallymimics an area of the retention element 16 facing toward the movableblade 12. Explaining further, as shown in FIG. 7D, retention element 16may provide a contact area 236 extending proximate the periphery ofaperture 232, as well as near the region of both the upper and lowerends thereof. Accordingly, it may be appreciated that the contact area236, defined by a generally oval shape from which apertures 232, 234,and 235 have been removed, of spacing element 230, as shown in FIG. 7D,substantially mimics the contact surface of movable blade 12 facingtoward spacing element 230. Of course, a cross-sectional contact area ofspacing element 230 may be tailored to match the cross-sectional sizeand shape of the piston body of a movable blade with which it may beassembled.

Alternatively, if a spacing element is undesirable, as shown in FIG. 7C,a lateral thickness X of movable blade 12 may be selected and movableblade 12 may be configured for exhibiting a selected outermost radial orlateral position. Further, the present invention contemplates that amovable blade within an expandable reamer of the present invention maybe replaced by a differently configured movable blade, as may bedesired.

Of course, many alternatives are contemplated by the present inventionin relation to a movable blade extending through the expandable reamer.For instance, a movable blade of an expandable reamer of the presentinvention may be moved laterally outwardly by way of at least oneintermediate piston element. In one embodiment as shown in FIG. 8A, apressurization sleeve may be configured for actuating at least onemovable blade of an expandable reamer while maintaining the cleanlinessand functionality of the at least one movable blade thereof. Forexample, FIG. 8A shows a partial side cross-sectional view of anexpandable reamer 310 of the present invention including movable blade312 outwardly spaced from the centerline or longitudinal axis 311 of thetubular body 332 (comprising upper tubular body section 332A and lowertubular body section 332B), affixed therein by way of retention elements316 and carrying cutting elements 336. Also, a nozzle 160 is shown inFIG. 8A positioned below movable blade 312 and oriented at an angle withrespect to longitudinal axis 311 so as to direct drilling fluid thatflows therethrough toward cutting elements 336 carried by movable blade312, when movable blade 312 is positioned at a laterally outermostposition.

Tubular body 332 includes a bore 331 therethrough for conductingdrilling fluid as well as a male-threaded pin connection 309 and afemale-threaded box connection 308. As shown in FIG. 8A, expandablereamer 310 may include a pressurization sleeve 340 having a reducedcross-sectional orifice 341 and may also include sealing elements 343A,343B, 345A, and 345B positioned between the pressurization sleeve 340and the tubular body 332. Reduced cross-sectional orifice 341 may besized for producing a selected magnitude of force as in relation to amagnitude of a flow rate of drilling fluid passing therethrough. Also,an annular chamber 346 may be formed between pressurization sleeve 340and tubular body 332, while another chamber 348 may be formed withintubular body 332, in communication with piston element 349. Pistonelement 349 may be effectively sealed within upper tubular body section332A by way of sealing element 352. Such a configuration maysubstantially inhibit drilling fluid from contacting the inner surface321 of movable blade 312.

Thus, during operation, drilling fluid may force (via fluid drag,pressure, momentum, or a combination thereof) the pressurization sleeve340 longitudinally downwardly, while a fluid (e.g., oil, water, etc.)within chamber 348 may become pressurized in response thereto. Further,biasing element 344 may resist the downward longitudinal displacement ofpressurization sleeve 340 while in contact therewith. Of course, biasingelement 344 may cause the pressurization sleeve 340 to returnlongitudinally upwardly if the magnitude of the downward force caused bythe drilling fluid passing through the reduced cross-sectional orifice341 of the pressurization sleeve 340 is less than the upward force ofthe biasing element 344 thereon. Additionally, a valve apparatus 333 maybe configured for selective control of communication between the annularchamber 346 and chamber 348. For example, valve apparatus 333 may beconfigured for preventing hydraulic communication between annularchamber 346 and chamber 348 until a minimum selected pressure magnitudeis experienced within annular chamber 346. Alternatively, valveapparatus 333 may be configured for allowing hydraulic communicationbetween annular chamber 346 and chamber 348 in response to a user inputor other selected condition (e.g., a minimum magnitude of pressuredeveloped within annular chamber 346). Accordingly, movable blade 312may remain positioned laterally inwardly until valve apparatus 333allows hydraulic communication between annular chamber 346 and chamber348.

Explaining further, once communication between annular chamber 346 andchamber 348 is allowed, pressure acting on piston element 349 may causemovable blade 312 to move laterally outwardly, against blade-biasingelements 324 and 326. Thus, piston element 349 may be forced againstmovable blade 312 in response to sufficient pressure communicated tochamber 348. Once movable blade 312 is positioned at a suitable lateralposition, reaming of a subterranean formation may be performed.Optionally, a shear pin (not shown) or other friable element (not shown)may restrain at least one of pressurization sleeve 340 in its initiallongitudinal position and movable blade 312 in its initial lateralposition, as shown in FIG. 8A.

Alternatively, instead of a pressurization sleeve that transmits orcommunicates a fluid in communication with a movable blade, a movableblade may be displaced by a pressure source that pressurizes a fluid orgas in communication with the movable blade. For instance, in referenceto FIG. 8B, an expandable reamer 310 is shown that is generally asdescribed above in relation to FIG. 8A but without upper tubular bodysection 332A. Explaining further, pressurized fluid or gas may becommunicated to chamber 348 by way of a pressure source 360. Pressuresource 360 may comprise a downhole pump or turbine operably coupled tovalve apparatus 333 and for communicating a pressurized fluidtherethrough. Also, valve apparatus 333 may be selectively andreversibly operated. For instance, valve apparatus may comprise asolenoid actuated valve as known in the art. Accordingly, movable blade312 may be deployed by way of pressurized fluid from pressure source360. Such a configuration may allow for expandable reamer 310 to beexpanded substantially irrespective of drilling fluid flow rates orpressures. Of course, many configurations may exist where the movableblades may communicate with a nondrilling fluid pressurized by adownhole pump or turbine. For instance, an expandable reamer may beconfigured as shown in any embodiments including an actuation sleeve asshown hereinabove, wherein the actuation sleeve is fixed in a positionfor separating drilling fluid from communication with any movable bladesand a port may be provided to pressurize the movable blades.

In another aspect of the present invention, at least one frangibleelement may be employed for selectively allowing or preventing drillingfluid communication with a movable blade of an expandable reamer. In oneexample, FIG. 8C shows an enlarged side cross-sectional view of amovable blade 312B of an expandable reamer of the present invention(e.g., an expandable reamer as shown in FIGS. 1A-1E), positioned withina recess formed in upper tubular body section 32A. Further, the at leastone frangible element 356 (e.g., at least one burst disc) may bepositioned within upper tubular body section 32A. Thus, at least onefrangible element 356 may be structured for failing in response to atleast a selected pressure within bore 31 of the expandable reamer beingexperienced. Accordingly, when the at least one frangible element 356fails, bore 31 and inner surface 321 may hydraulically communicate,which may, as described hereinabove, cause movable blade 312B to movelaterally outward, against the forces of blade-biasing elements 24 and26.

In a further embodiment contemplated by the present invention, drillingfluid may act upon at least one intermediate piston element for moving amovable blade of an expandable reamer of the present invention. In oneexemplary embodiment, as shown in FIG. 8D, intermediate piston element372 may be configured for displacing movable blade 312C. In furtherdetail, intermediate piston element 372 may be positioned within acavity formed in upper tubular body section 32A and sealed thereagainstby sealing element 379. Further, protrusions 374A, 374B, and 374C mayextend from piston element 372 through apertures 376A, 376B, and 376C,respectively, that are formed in upper tubular body section 32A andtoward inner surface 321 of movable blade 312C. Explaining further,pressure acting on inner surface 377 of intermediate piston element 372,causing protrusions 374A, 374B, and 374C to contact the inner surface321 of movable blade 312C, which may cause movable blade 312C to movelaterally outwardly against blade-biasing elements 24 and 26. Of course,movable blade 312C may be structured in relation to contact areas ofprotrusions 374A, 374B, and 374C with inner surface 321. Once movableblade 312C is positioned at a suitable lateral position, reaming of asubterranean formation may be performed. Such a configuration may beadvantageous for inhibiting contact between drilling fluid and movableblade 312C.

In a further aspect contemplated by the present invention, drillingfluid may act upon a plurality of intermediate piston elements formoving a movable blade of an expandable reamer of the present invention.In an exemplary embodiment, as shown in FIG. 8E, intermediate pistonelements 382A, 382B, and 382C may be configured for displacing movableblade 312D. Also, movable blade 312D may be recessed for accommodatingat least a portion of each of intermediate piston elements 382A, 382B,and 382C. Each of sealing elements 383A, 383B, and 383C may beassociated with each of intermediate piston elements 382A, 382B, and382C, respectively, and may be configured for sealing engagement betweeneach of intermediate piston elements 382A, 382B, and 382C and tubularbody 332. Such a configuration may provide a relatively compact designfor displacing movable blade 312D.

Thus, during operation, intermediate piston elements 382A, 382B, and382C may extend through respective apertures 386A, 386B, and 386C formedin upper tubular body section 32A and toward inner surface 321D ofmovable blade 312D. Explaining further, pressure acting on each ofintermediate piston elements 382A, 382B, and 382C through ports 384A,384B, and 384C may cause intermediate piston elements 382A, 382B, and382C to contact the inner surface 321D of movable blade 312D, which maycause movable blade 312D to move laterally outwardly, againstblade-biasing elements 24 and 26. Of course, movable blade 312D may bestructured in relation to contact areas of intermediate piston elements382A, 382B, and 382C against inner surface 321D. Once movable blade 312Dis positioned at a suitable lateral position, reaming of a subterraneanformation may be performed.

The present invention further contemplates that a movable blade may bestructured for returning laterally inwardly even if blade-biasingelements 24 and 26 fail to cause a movable blade do so. Particularly,FIG. 9A shows movable blade 12 positioned within an intermediate element4 and affixed thereto by way of at least one frangible element, forinstance, shown as two shear pins 6. Further, intermediate element 4 maybe affixed to upper tubular body section 32A by way of lock rods (e.g.,lock rods 106 as shown in FIG. 4C). Thus, movable blade 12 may operategenerally as described above, however, if movable blade 12 becomes stuckin an outward lateral position, a laterally inward force applied tomovable blade 12 may cause the at least one frangible element, in thisembodiment shown as two shear pins 6, to fail, which, in turn, may allowmovable blade 12 as well as retention element 16B to move laterallyinwardly. For example, shear pins 6 may be caused to fail by moving theexpandable reamer (e.g., expandable reamer 10, as shown in FIGS. 1A-1E)longitudinally (i.e., under a longitudinal force) into a bore that issmaller than the nominal size of the expandable reamer 10 in an at leastpartially expanded condition. Contact between the movable blade 12 and abore (e.g., a casing or borehole) of a smaller size may generatesignificant inward lateral force sufficient to fail shear pins 6. Such aconfiguration may provide an alternative manner for causing movableblade 12 to move laterally inwardly other than by blade-biasing elements24 and 26. Of course, shear pins 6 may be structured to resistanticipated forces that may be experienced during reaming operationswithout failing.

In another aspect of the present invention, FIG. 9B shows a movableblade 12M configured to in move in a direction substantially parallel toaxis V (i.e., non-perpendicular to longitudinal axis 11, which isoriented at an angle φ with respect to horizontal axis H. Such aconfiguration may be advantageous for forcing movable blade 12M from anexpanded position laterally inwardly if blade-biasing elements 24M and26M fail to do so. As mentioned hereinabove, “lateral” or “radial,” asused herein, encompasses a direction of movement of a movable blade thatis at least partially longitudinal, as is shown in FIG. 9B. Explainingfurther, a longitudinal downward force which is applied to movable blade12M may cause movable blade 12M to move laterally inwardly because aportion of the longitudinal downward force may be resolved in alaterally inward direction along the mating surfaces between movableblade 12M and retention element 16M. Thus, by moving an expandablereamer (e.g., expandable reamer 10 as shown in FIGS. 1A-1E)longitudinally upwardly within a subterranean borehole or other borethat is smaller than an expanded diameter of the expandable reamer(e.g., a casing or other tubular element positioned within asubterranean borehole), a movable blade 12M may impact or become wedgedtherein. Continuing to pull upward upon the expandable reamer 10 maycause a substantial downward longitudinal force to be applied to movableblade 12M, which may also develop a substantial inward lateral force,thus displacing movable blade 12M laterally inward and allowing theexpandable reamer 10 to continue longitudinally upward within the bore(not shown).

Also, it may be appreciated that fabrication of movable blade 12M may befacilitated by forming a blade plate 13B that is affixed to an angledmovable blade body 13A. For instance, it may be advantageous to weld ormechanically affix (e.g., via bolts or other threaded fasteners) bladeplate 13B to angled movable blade body 13A. Such a configuration maysimplify fabrication of movable blade 12M.

The present invention further contemplates that at least a portion of asurface of an expandable reamer may be covered or coated with a materialfor resisting abrasion, erosion, or both abrasion and erosion.Generally, a substantial portion of the exterior of an expandable reamermay be configured for resisting wear (e.g., abrasion, erosion, contactwear, or combinations thereof). In one embodiment, hardfacing materialmay be applied to at least one surface of an expandable reamer, whereinat least two different hardfacing material compositions are utilized andspecifically located in order to exploit the material characteristics ofeach type of hardfacing material composition employed. The use ofmultiple hardfacing material compositions may further be employed as awear-resistant coating on various elements of the expandable reamer. Thesurfaces to which hardfacing material is applied may include machinedslots, cavities or grooves providing increased surface area forapplication of the hardfacing material. Additionally, such surfacefeatures may serve to achieve a desired residual stress state in theresultant hardfacing material layer or other structure.

For example, one surface that may be configured for resisting wear mayinclude an exterior surface S of bearing pads 34 and 38, as shown inFIG. 1A. With respect to surface S, bearing pads 34 and 38 may comprisehardfacing material, diamond, tungsten carbide, tungsten carbide bricks,tungsten carbide matrix, or superabrasive materials. The presentinvention further contemplates that surface S may comprise at least onehardfacing material. A hardfacing material, as known in the art and asused herein, refers to a material formulated for resisting wear.Hardfacing materials may include materials deposited by way offlame-spraying, welding, via laser beam heating, or as otherwise knownin the art. Optionally, hardfacing material may be applied according toa so-called “graded-composite” process, as known in the art. Morespecifically, different types of hardfacing material may be applied upona portion of a surface of an expandable reamer adjacent to one another,or at least partially superimposed with respect to one another, or both.

Exemplary materials and processes for forming hardfacing material aredisclosed in U.S. Pat. No. 6,651,756 to Costo, Jr. et al., assigned tothe assignee of the present invention, the disclosure of which isincorporated, in its entirety, by reference herein. In oneconfiguration, hardfacing material may generally include some form ofhard particles delivered to a surface via a welding delivery system(e.g., by hand, robotically, or as otherwise known in the art). Hardparticles may come from the following group of cast or sintered carbides(e.g., monocrystalline) including at least one of chromium, molybdenum,niobium, tantalum, titanium, tungsten, and vanadium and alloys andmixtures thereof. RE 37,127 of U.S. Pat. No. 5,663,512 to Schader etal., assigned to the assignee of the present invention, the disclosureof which is incorporated herein in its entirety by this reference,discloses, by way of example and not by limitation, some exemplaryhardfacing materials and some exemplary processes that may be utilizedby the present invention. Other hardfacing materials or processes, asknown in the art, may be employed for forming hardfacing material uponan expandable reamer of the present invention.

For example, sintered, macrocrystalline, or cast tungsten carbideparticles may be captured within a mild steel tube, which is then usedas a welding rod for depositing hardfacing material onto the desiredsurface, usually, but optionally, in the presence of a deoxidizer, orflux material, as known in the art. The shape, size, and relativepercentage of different hard particles may affect the wear and toughnessproperties of the deposited hardfacing, as described by RE 37,127 toSchader et al. For example, a relatively hard (e.g., having a relativelyhigh percentage of tungsten carbide) may be applied on at least aportion of a gage surface of the expandable reamer, while at least aportion of a non-gage surface of the expandable reamer may be coatedwith a so-called macrocrystalline tungsten carbide hardfacing material.

Additionally, U.S. Pat. No. 5,492,186 to Overstreet et al., assigned tothe assignee of the present invention, the disclosure of which isincorporated herein in its entirety by this reference, describes abi-metallic gage hardfacing configuration for heel row teeth on a rollercone drill bit. Thus, the characteristics of a hardfacing material maybe customized to suit a desired function or environment associated witha particular surface of an expandable reamer of the present invention.

Additionally or alternatively, other known materials for resisting wearof a surface, including surface hardening (e.g., nitriding), ceramiccoatings, or other plating processes or materials may be employed uponat least a portion of a surface of an expandable reamer according to thepresent invention.

In a further aspect of bearing pads 34 and 38, a hardfacing pattern maybe formed thereon. More particularly, FIG. 10A shows an enlarged view ofa portion of expandable reamer 10 including bearing pads 34 and 38.According to the present invention, at least lower longitudinal regions58 and 59L of at least one of bearing pads 34 and 38 may include ahardfacing pattern formed thereon. Explaining further, during use, anexpandable reamer may include a pilot bit installed on a leadinglongitudinal end thereof. Further, such a pilot drill bit may be usedfor drilling, for instance, through a cementing shoe or into asubterranean formation. Even though a pilot bit may be sized fordrilling a subterranean borehole large enough for the expandable reamerto pass through when the at least one movable blade thereof is notexpanded, abrasive wear may occur on the bearing surfaces of theexpandable reamer 10, for instance, surfaces S of the bearing pads 34and 38. In addition, wear may occur on the movable blades (not shown),despite being positioned at its laterally innermost position, due toexcessive contact with the borehole formed by a pilot drill bit.

Therefore, the present invention contemplates that hardfacing patternssuch as those shown in FIGS. 10B-10B may be utilized upon the lowerlongitudinal regions 58 and 59L of at least one of bearing pads 34 and38. In further detail, FIGS. 10B-10B each show a view of bearing pad 34in a direction as shown in FIG. 10A by reference lines C-C. As shown ineach of FIGS. 10B-10E, a plurality of protruding ridges 64 ofwear-resistant material (e.g., hardfacing, diamond, or otherwear-resistant material as known in the art) may be positioned inalternating or overlapping relationships, or otherwise oriented asdesired, without limitation, upon a surface of bearing pad 34. Putanother way, the plurality of protruding ridges 64 may be separated bygaps or recesses 65. Such a configuration may provide a surface havingsubstantial wear resistance, but also may exhibit a reaming or drillingcapability during rotation of an expandable reamer. Thus, duringoperation, the plurality of protruding ridges 64 may precede the portionof expandable reamer longitudinally thereabove and may remove portionsof the borehole that may otherwise excessively contact and wear theexpandable reamer, thus providing a degree of protection thereto.

Further, optionally, at least a portion of an expandable reamer of thepresent invention may be coated with an adhesion-resistant coating, suchas a relatively low adhesion, preferably nonwater-wettable surface asdisclosed by U.S. Pat. No. 6,450,271 to Tibbitts et al., which isassigned to the assignee of the present invention and the disclosure ofwhich is incorporated in its entirety by reference herein. Moreparticularly, at least a portion of a surface of an expandable reamermay include a material providing reduced adhesion characteristics forsubterranean formation material in relation to a surface that does notinclude the material. Particularly, it may be desirable for anadhesion-resistant coating to exhibit a relatively high shale releaseproperty. Further, such an adhesion-resistant coating may exhibit asurface finish roughness of about 32μ inches or less, RMS. Also, such anadhesion-resistant coating may exhibit a sliding coefficient of frictionof about 0.2 or less. One exemplary material for an adhesion-resistantcoating may include a vapor-deposited, carbon-based coating exhibiting ahardness of at least about 3000 Vickers. In a further aspect, anadhesion-resistant coating may exhibit a surface having lowersurface-free energy and reduced wettability by at least one fluid incomparison to an untreated portion of a surface of an expandable reamer.Such a configuration may inhibit adhesion of formation cuttings carriedby the drilling fluid with a surface having the adhesion-resistantcoating. Exemplary materials for an adhesion-resistant coating mayinclude at least one of: a polymer, a PTFE, a FEP, a PFA, a ceramic, ametallic material, and a plastic, a diamond film, monocrystallinediamond, polycrystalline diamond, diamond-like carbon, nanocrystallinecarbon, vapor-deposited carbon, cubic boron nitride, and siliconnitride.

In yet a further aspect of the present invention, cutting elements anddepth-of-cut-limiting features positioned upon a movable blade of anexpandable reamer may be configured as disclosed in U.S. Pat. Nos.6,460,631 and 6,779,613, both to Dykstra et al. Such a configuration maybe advantageous for directionally reaming a borehole in a subterraneanformation. Conventional depth-of-cut configurations for drill bits maybe, at least in part, known and included by so-called “EZSteer”technology, which is commercially available for drill bits from HughesChristensen Company of Houston, Tex.

In further detail, a movable blade may include a bearing surfaceconfigured for inhibiting a rotationally following (or preceding)cutting element from overengaging a subterranean formation andpotentially damaging the cutting element. FIG. 11A shows a movable blade12 having bearing surfaces 86A and 86B configured for inhibiting arotationally following (or preceding) cutting element from overengaginga subterranean formation. Of course, at least one of bearing surfaces86A and 86B may include any depth-of-cut control (DOCC) features asdisclosed within U.S. Pat. Nos. 6,460,631 and 6,779,613, both to Dykstraet al., or as otherwise known in the art, without limitation.

Additionally, optionally, wear knots or other bearing structures may beformed upon a movable blade or an expandable reamer. For example, FIG.11B shows a movable blade 12F including a plurality of thedepth-of-cut-limiting features, each comprising an arcuate bearingsegment 88. Specifically, regions 88A and 88B including bearing segments88 may each reside at least partially on movable blade 12F. The arcuatebearing segments 88, each of which lies substantially along the sameradius from the bit centerline as a cutting element (not shown) thatrotationally trails that bearing segment 88, respectively, together mayprovide sufficient surface area to withstand the axial or longitudinalweight-on-bit (or weight-on-reamer) without exceeding the compressivestrength of the formation being drilled, so that the rock does notunduly indent or fail and the penetration of cutting element (not shown)into the rock is substantially controlled. Further, such a configurationmay also substantially limit torque-on-bit experienced by the expandablereamer. Such a configuration may substantially limit the depth-of-cutthat may be achieved with the expandable reamer, which may inhibit orprevent damage to a cutting element due to an excessive depth of cut.

Further, the present invention contemplates that a depth-of-cut-limitingfeature or other aspects disclosed herein related to a geometry orconfiguration of a movable blade may be employed upon reamers havingfixed blades, such as reaming-while-drilling (RWD) tools. U.S. Pat. Nos.6,739,416 and 6,695,080 both to Presley, et al., both assignee of thepresent invention, disclosures of which are incorporated herein in theirentirety by this reference, disclose exemplary RWD tools.

Although the foregoing description contains many specifics, these shouldnot be construed as limiting the scope of the present invention, butmerely as providing illustrations of some exemplary embodiments.Similarly, other embodiments of the invention may be devised that do notdepart from the spirit or scope of the present invention. Features fromdifferent embodiments may be employed in combination. The scope of theinvention is, therefore, indicated and limited only by the appendedclaims and their legal equivalents, rather than by the foregoingdescription. All additions, deletions, and modifications to theinvention as disclosed herein, which fall within the meaning and scopeof the claims, are to be embraced thereby.

1. An expandable reamer apparatus for subterranean drilling, comprising:a tubular body having a longitudinal axis and a drilling fluid flow paththerethrough; a plurality of generally radially and longitudinallyextending blade structures carried by the tubular body, the plurality ofblade structures each comprising a movable blade having a lateral heightand carrying cutting structures thereon, and wherein each moveable bladeis replaceable by blades having a different lateral height; at least oneblade-biasing element for holding the movable blades of the plurality ofblade structures at an innermost lateral position with a force; and anactuation sleeve positioned along an inner diameter of the tubular bodyand configured to selectively allow pressure of drilling fluid withinthe drilling fluid flow path of the tubular body to move the movableblades of the plurality of blade structures outwardly against the forcein response to an actuation device engaging the actuation sleeve at alower end thereof below the plurality of blade structures, the actuationsleeve further comprising at least one aperture through a side wallthereof above a location for engagement of the actuation devicetherewith.
 2. The apparatus of claim 1, wherein each of the plurality ofblades is substantially circumferentially symmetrically disposed aboutthe tubular body.
 3. The apparatus of claim 1, wherein the actuationsleeve is positioned within the tubular body to selectively allowpressure of drilling fluid in the drilling fluid flow path to effectmovement of the movable blades of the plurality of blade structures. 4.The apparatus of claim 1, further comprising a pilot drill bit disposedbelow the tubular body.
 5. The apparatus of claim 1, wherein the cuttingstructures comprise polycrystalline diamond compact cutting elements. 6.The apparatus of claim 1, wherein the blades having a different lateralheight are of a different configuration than the blades having a lateralheight.
 7. An expandable reamer apparatus for subterranean drilling,comprising: a tubular body having a longitudinal axis and a drillingfluid flow path therethrough; a plurality of generally radially andlongitudinally extending blade structures carried by the tubular body,the blade structures each comprising a movable blade having a lateralheight and carrying cutting structures thereon, and wherein eachmoveable blade is replaceable by blades having a differentconfiguration; at least one blade-biasing element for holding themovable blades of the plurality of blade structures at an innermostlateral position with a force; and an actuation sleeve positioned alongan inner diameter of the tubular body and configured to selectivelyallow pressure of drilling fluid within the drilling fluid flow path ofthe tubular body to move the movable blades of the plurality of bladestructures outwardly against the force in response to an actuationdevice engaging the actuation sleeve at a lower end thereof below theplurality of blade structures, the actuation sleeve further comprisingat least one aperture through a side wall thereof above a location forengagement of the actuation device therewith.
 8. The apparatus of claim7, wherein the plurality of blades are substantially circumferentiallysymmetrically disposed about the tubular body.
 9. The apparatus of claim7, further comprising an actuation structure positioned within thetubular body and adapted to selectively allow drilling fluid therein toeffect movement of the movable blades of the plurality of bladestructures.
 10. The apparatus of claim 7, further comprising a pilotdrill bit disposed below the tubular body.